A familiar is a normal animal that gains new powers and becomes a magical beast when summoned to service by a sorcerer or wizard. It retains the appearance, Hit Dice, base attack bonus, base save bonuses, skills, and feats of the normal animal it once was, but it is treated as a magical beast instead of an animal for the purpose of any effect that depends on its type. Only a normal, unmodified animal may become a familiar. An animal companion cannot also function as a familiar. A familiar also grants special abilities to its master (a sorcerer or wizard), as given on the table below. These special abilities apply only when the master and familiar are within 1 mile of each other. Levels of different classes that are entitled to familiars stack for the purpose of determining any familiar abilities that depend on the master’s level. Most Familiars are of the animal type. Celestial and fiendish templates make the familiar's type a magical beast. There are improved familiars of other types as well. The best types you can acquire are those that don't depend on many HD, because familiars don't gain bonus HD.

What to look on a familiar?

Disclaimer: All of the following information come from http://www.d20srd.org/  

Statistics: Familiars benefit from high strength if used in combat. Dexterity is important if you use your familiar as a scout or to deliver touch spells, along with weapon finesse. Intelligence goes up as your familiar gains bonus abilities. Completely dump wisdom as your familiar will be using your base will save and most animals have high spot/listen ratings. Charisma is interestingly an important stat. It is used for use magic device, so combined with the ability to speak, your familiar will be using wands.
Speech: It is great if your familiar speaks. It has interesting role playing possibilities, can provide nice information and gives it the ability to use wands.
Skills: Look for high spot and listen checks. Also hide and move silently can be greatly appreciated. Remember that your familiar will be using your own ranks, so plan your skills so that your skills do not overlap. Additionally, keep an eye for racial modifiers to skills.
Feats: Feats like power attack, improved initiative, weapon finesse, alertness, dodge and track are feats that even though are common, can provide nice bonuses to you and your familiar.
Special Abilities: Try to find abilities that give bonuses to as many people you can. Area and at will effects are very nice. Also look for spells that don't depend on caster level.

Familiar Basics

Use the basic statistics for a creature of the familiar’s kind, but make the following changes:

Hit Dice: For the purpose of effects related to number of Hit Dice, use the master’s character level or the familiar’s normal HD total, whichever is higher.
Hit Points: The familiar has one-half the master’s total hit points (not including temporary hit points), rounded down, regardless of its actual Hit Dice.
Attacks: Use the master’s base attack bonus, as calculated from all his classes. Use the familiar’s Dexterity or Strength modifier, whichever is greater, to get the familiar’s melee attack bonus with natural weapons. Damage equals that of a normal creature of the familiar’s kind.
Saving Throws: For each saving throw, use either the familiar’s base save bonus (Fortitude +2, Reflex +2, Will +0) or the master’s (as calculated from all his classes), whichever is better. The familiar uses its own ability modifiers to saves, and it doesn’t share any of the other bonuses that the master might have on saves.
Skills: For each skill in which either the master or the familiar has ranks, use either the normal skill ranks for an animal of that type or the master’s skill ranks, whichever are better. In either case, the familiar uses its own ability modifiers. Regardless of a familiar’s total skill modifiers, some skills may remain beyond the familiar’s ability to use.

Familiar Ability Descriptions

All familiars have special abilities (or impart abilities to their masters) depending on the master’s combined level in classes that grant familiars, as shown on the table below. The abilities given on the table are cumulative.


Natural Armor Adj: The number noted here is an improvement to the familiar’s existing natural armor bonus.
Int: The familiar’s Intelligence score.
Alertness (Ex): While a familiar is within arm’s reach, the master gains the Alertness feat.
Improved Evasion (Ex): When subjected to an attack that normally allows a Reflex saving throw for half damage, a familiar takes no damage if it makes a successful saving throw and half damage even if the saving throw fails.
Share Spells: At the master’s option, he may have any spell (but not any spell-like ability) he casts on himself also affect his familiar. The familiar must be within 5 feet at the time of casting to receive the benefit. If the spell or effect has a duration other than instantaneous, it stops affecting the familiar if it moves farther than 5 feet away and will not affect the familiar again even if it returns to the master before the duration expires. Additionally, the master may cast a spell with a target of "You" on his familiar (as a touch range spell) instead of on himself. A master and his familiar can share spells even if the spells normally do not affect creatures of the familiar’s type (magical beast).
Empathic Link (Su): The master has an empathic link with his familiar out to a distance of up to 1 mile. The master cannot see through the familiar’s eyes, but they can communicate empathically. Because of the limited nature of the link, only general emotional content can be communicated. Because of this empathic link, the master has the same connection to an item or place that his familiar does.
Deliver Touch Spells (Su): If the master is 3rd level or higher, a familiar can deliver touch spells for him. If the master and the familiar are in contact at the time the master casts a touch spell, he can designate his familiar as the "toucher." The familiar can then deliver the touch spell just as the master could. As usual, if the master casts another spell before the touch is delivered, the touch spell dissipates.
Speak with Master (Ex): If the master is 5th level or higher, a familiar and the master can communicate verbally as if they were using a common language. Other creatures do not understand the communication without magical help.
Speak with Animals of Its Kind (Ex): If the master is 7th level or higher, a familiar can communicate with animals of approximately the same kind as itself (including dire varieties): bats with bats, rats with rodents, cats with felines, hawks and owls and ravens with birds, lizards and snakes with reptiles, toads with amphibians, weasels with similar creatures (weasels, minks, polecats, ermines, skunks, wolverines, and badgers). Such communication is limited by the intelligence of the conversing creatures.
Spell Resistance (Ex): If the master is 11th level or higher, a familiar gains spell resistance equal to the master’s level + 5. To affect the familiar with a spell, another spellcaster must get a result on a caster level check (1d20 + caster level) that equals or exceeds the familiar’s spell resistance.
Scry on Familiar (Sp): If the master is 13th level or higher, he may scry on his familiar (as if casting the scrying spell) once per day.

When choosing a familiar, remember that it isn't there only to provide the mild bonus. It has special qualities, skill points and even feats you can work with to improve your character. Here's an overview of the basic familiars in the PHB:

Bat: The bonus to listen checks may not be much, but this has blindsense as a special quality. That means that effectively you get blindsense if you choose your bat to deliver your touch spell to the invisible target. It can be an effective scout at early to mid levels, as it has nice bonuses to spot/listen, hide/move silently and low light vision.
Cat: Cats aren't that good for familiars. They can't fly, their stats are average and only get scent and weapon finesse. They give bonuses to move silently which is mild. However they have a bigger list of skills than other familiars.
Hawk: Fly speed 60ft, nice stats and weapon finesse. Also a companion with spot +14 at 1st level is nothing to scoff at. Great familiar, especially for delivering touch attacks.
Lizard: Not good movement modes, bad stats, weapon finesse as a feat without great dexterity and you can live without the +3 on climb checks.
Owl: As with the hawk, but trades 20ft of fly speed for a huge bonus to move silently, listen checks and spot checks. Can be used as an effective scout, especially in areas of shadowy illumination. The granted ability isn't too nice though, because it is situational.
Rat: Quite the skill-monkey. Skill mastery, more movement modes, weapon finesse but not good stats. The granted ability is awesome. Also has scent.
Raven: It isn't much, bad skills and stats and no special abilities. However it flies and speaks one language, probably making it able to activate spell-trigger items if his master has sufficient UMD ranks.
Snake: As per rat, but trades some skill ranks for a crappy DC poison. The granted ability has its uses, but i think the rat's is better.
Toad: If you take this, do it only for its granted ability. It's useless because it has only a 5ft speed, even though its hide skill is pretty buffed up.
Weasel: The granted ability is good, but it doesn't fly and doesn't have nice special abilities or skills. If it attacks, you probably have a familiar with a death wish . May fit thematically with necromancers.

Classes

Classes that grant familiars:

Wizard/Sorcerer PHB: These are the most common familiars and unfortunately, the weakest. The classes have bad hit points, BAB and saves, making them less useful in battle situations.
Hexblade CW: Very nice class for a familiar. Hexblades are a full BAB and high hit die class, augmenting your familiar to nearly the maximum.
Dread Necromancer HoH: Better familiars due to higher hit die compared to that of the wizard. Also they get a different selection of familiars.
Nar Demonbinder UE: Gets an improved familiar. Sorcerer/wizard and Nar Demonbinder levels stack to determine familiar abilities.
Celebrant of Sharess PGtF: Easy requirements and the familiar benefits at double the prestige class levels for the granted abilities.

Classes that stack for familiar abilities:

Alienist CA: Stacks for familiar abilities and it later acquires the pseudonatural template.
Arcane Heirophant RotW: Your animal companion becomes your familiar.
Fleshwarper LoM: Your familiar becomes an aberration and it gains new abilities.

Classes that benefit from Obtain Familiar:

Duskblade PHB II: Full BAB, some physical skills, ok hit die. However you won't probably have your familiar deliver your touch spells.
Beguiler PHB II: Great skills, buff spells, higher hit die than normal sorcerers. Grab a raven familiar and give it a wand. It will probably be able to use it if you are high enough level.
Bard PHB: As above, but better. Medium BAB actually helps. Also the spell list is wider and your familiar can be very helpful in situations like delivering healing spells in the battlefield, buffed by your personal range spells etc.
Gish: While their familiars' abilities may be lower than normal, they do acquire some nice skills, have better BAB than normal and their hit dice are higher usually. Also most of the times these characters buff up pre combat, which benefits a familiar greatly.
Warlock CA: Although your familiar can't really deliver your spells or benefit from buffs, you have UMD and several other nice skills.
Dragonfire Adept DM: Ok hit die, nice skills and good saves. BAB hurts though.

Feats

Mounted Combat PHB: This is usually combined with high ride skill and improved familiars. Protecting your familiar from blows is nothing to scoff at.
Toughness PHB: Don't even consider it for a HP - pump to your familiar :D.
Improved Familiar various: Provides very nice options. A list of the best improved familiars will be included in the guide later.
Improved Toughness CW: This is actually nice. The bonus HP are quite a few.
Obtain Familiar CA: So you gain a familiar, with abilities based on your level? With a feat? Take a look at the sorcerer class. They hardly have any class features besides summon familiar.
Bonded Familiar PHB II: Either way you lose experience. Of course it would be best if you didn't come in a situation to receive a deadly blow, but this feat is like 2/day avoid XP loss from death.
Combat Familiar PHB II: This isn't nice, but it's required if your familiar is of small size and must be in the same square with the target to touch him.
Lurking Familiar PHB II: Not so good. Requires combat familiar, which makes it unattractive. Also you need a familiar that can hide. This feat is effective when facing opponents that will get screwed if they lose their dexterity bonus to AC.
Spell-linked Familiar PHB II: Your familiar gets an amount of your spells. Chose some that are capped out or that don't benefit from caster level. This feat essentially grants you extra actions in combat. Don't neglect this.
Celestial Familiar BoED: As with improved familiar, this will be examined later.
Dragon Familiar Draconomicon: Get a wyrmling dragon as a familiar. Great.
Planar Familiar PlH: Offers some choices as improved familiar.
Stitched Spell Familiar LM: Nice option for necromancers.

There is of course to edit some of your familiar's feats and skills, here's how: The power Psychic Reformation lets you tweak the subject's skills, feats or powers. Now most of the times your familiar won't even have powers, but the other two aspects are worth tweaking. Feats like track on a familiar that has scent (such as a rat), power attack, point blank shot, skill focus (Use Magic Device) are great options. Remember that in order to redistribute skill points, you can only re-spend them on class skills. A single use of psychic reformation can probably be bought, paying approximately 500 gp (assuming the cost is power level x manifester level x 25 gp). The XP cost can be translated to gp by paying 5 gp for each XP spend by the manifester (which is actually half, since you are going to spend some, too). Thus the XP cost is 125 x reformed HD. To add more to this, you can get the alternative feature drakken familiar. Your familiar now has the dragonblood subtype and if you give it the draconic aura feat, you can select a broad range of auras to help you and your party.

Spells

Augment Familiar SC: It's a +4 bonus to strength, dexterity and constitution, damage reduction 5/magic and +2 resistance to all saving throws. It's a big buff for a second level spell.
Enhance Familiar SC: +2 competence bonus on saves, attack rolls, melee damage rolls and +2 dodge bonus to AC. Great duration.
Familiar Pocket SC: This unfortunately only can hide tiny or smaller familiars.
Fortify Familiar SC: 2d8 hit points, +2 enhancement bonus to natural armor, 25% fortification.
Imbue Familiar with Spell Ability SC: This is a very interesting spell. You can give some of your spells to your familiar. That way you gain actions, since the spells transferred are at the same caster level as yours. This may give your familiar to use wands without need of use magic device.

Spells to use via Share Spells

Arrow Mind SC: Nice for outsider familiars, who have martial weapon proficiency.
Aspect of the Earth Hunter SC: This is just great. Even a lowly lizard becomes a Bulette. Great stats, tremorsense, natural armor.
Bite of the Werebear SC: Great enhancement bonuses to nearly everything and gives you the ability to use power attack and blind fight.
Bite of the Wereboar SC: As above, but not as powerful.
Bite of the Wererat SC: This is great, since the level is really low. If you can actually persist it, it will affect your familiar for 24 hours. Also gain the benefits of weapon finesse, if your familiar lacks it.
Bite of the Weretiger SC: Pretty much the same with bite of the werebear.
Bite of the Werewolf SC: Nice, but meh. The other bites are better.
Blink/Improved PHB: Great defensive spells.
Bloodhound SC: For familiar trackers.
Body of War SC: Cast it on you and then dismiss it. Get a huge warforged familiar construct to smack your enemies.
Comprehend Languages PHB: Great for getting your familiar to scout and snoop around.
Contingency PHB: Essentially you get twice the spell levels you invest and protect both you and your familiar.
Displacer Form SC: Nice for familiars, but there are better forms.
Divine Sacrifice SC: If you can get yourself a wand of this and your familiar has fast healing or similar qualities, it will give high damage output.
Dragon Breath SC: Gives both you and your familiar a breath weapon. You get two applications of the spell at the cost of one essentially.
Dragonsight SC: Not only this is great by itself, but it makes your familiar great for delivering touch spells.
Dragonskin SC: Enhancement bonus to natural armor and variable energy resistance. Not much, but handy.
False Life PHB: It's an easy way for low level spellcasters to protect themselves and their familiars.
Fiendform SC: This doesn't seem much, but it has some hidden qualities. First of all your familiar's type becomes an outsider, which means that it gains proficiency with martial weapons. It also gains supernatural, extraordinary and spell-like abilities of the new form.
Find Traps PHB: If you can invest in disable device and search and don't have trapfinding, this spell can transform your familiar in a trapfinder.
Fist of Stone SC: Nice if you have a familiar with the multiattack feat. Great even without it.
Fire Whips SC: This gives you melee touch attacks that do 6d6 damage! Combined with high dexterity and weapon finesse can give you high attack roll so that you don't care about two-weapon fighting penalties.
Flight of the Dragon SC: Nice long distance flying speed and gives your familiar a flight speed.
Fly, Swift SC: Meh, 1 round flight as a swift action, may help but not worth its spell levels.
Focusing Chant SC: Nice little buff for early levels. Even helps UMD, hide, move silently, spot, listen and attack rolls.
Glibness SC: It would be interesting to see a raven bluffing a merchant :D:D.
Grace SC: Nice buff and you can stack dexterity bonus, since that's sacred. Also bonus to land speed, which isn't much. The good-aligned weapons though can really help.
Gutsnake SC: It's a nice spell, but a giant constrictor snake sprouting out of a rat's abdomen would be fun :D.
Haste, Swift SC: This is of personal range so it can affect your familiar and has a duration greater than 1 round. Also it is a swift action.
Improvisation SC: Great spell for familiars. You can use it to deliver an important touch spell or activate a magic item.
Invisibility, Superior SC: This is a great invisibility spell and it can affect your familiar.
Invisibility, Swift SC: As above, but the duration is crappy.
Iron Body PHB: Great duration and you can dismiss it. Also the bonuses are great for a familiar.
Kiss of the Vampire SC: Enervation or vampiric touch as a melee touch attack by both you and your familiar.
Lightfoot SC: Great if you want your familiar to deliver a spell through a horde of enemies via flyby attack or the like.
Lightning Ring SC: Double the damage output of lightning ring.
Lion's Charge SC: Great if your BAB is good.
Magic Fang, Superior SC: Very nice spell with personal range. Affects both your natural weapons and your familiar's.
Master's Touch SC: Gives your outsider familiars the ability to carry shields.
Mirror Image PHB: Is a huge buff and benefits are important to a combat familiar.
Moment of Prescience PHB: You effectively get two bonuses to your rolls, as most of the checks can be done by your familiar, too.
Mondekainen's Lucubration PHB: If this works with spells that your familiar can cast (through spells or feats) this is ok to have. You can regain any spell up to 5th level two times, so if you regain a 5th level spell of your own and a 1st or greater from your familiar, you essentially get 1-1 spell level trade.
Negative Energy Aura SC: If you and your familiar are both undead somehow, you get to heal one another, damage living creatures and heal other undead creatures that are probably around.
Nightshield SC: Great spell that grants bonuses to saving throws and blocks magic missiles.
Nightstalker's Transformation SC: Wow. Just wow. Great bonuses to stats, skills, AC, saves. Also proficiencies and weapon finesse, as well as evasion. Also 3d6 sneak attack dice! If you want to use magic items and spells, just dismiss it. Your familiar will still be a killer with this one.
Nimbus of Light SC: It's easy to get a wand out of this and you get two discharges at the cost of one.
Nixie's Grace SC: Very nice buff, but it's a little high in level. However the +8 enhancement bonus to charisma helps both his bard and his familiar.
Opalescent Glare SC: Two gaze attacks at the cost of one. Great for stacking fear effects.
Positive Energy Aura SC: As with negative energy aura.
Primal Form SC: Some defensive abilities and nice duration. Also low level.
Rary's Mnemonic Enhancer PHB: If you can use this with abilities like Spell-linked familiar feat, this is indeed great. You get 3*2 = 6 spell levels to use at the cost of just 4. Same goes with retain ability.
Ray Deflection SC: It the case thet your familiar gets targeted by rays regularly, this will provide it protection.
Ruin Delver's Fortune SC: Great, but you really need to find a way in casting it persistent. That way it will sit all day for both you and your familiar.
See Invisibility PHB: Great for familiar scouts.
Serene Visage SC: As with glibness.
Shapechange PHB: Great spell. The im-possibilities are endless :D.
Mental Pinnacle XPH: It's only blue because it's not dismiss-able. Otherwise you and your familiar gain the power of a psion of your caster level?! It's insane!
Heroics SC: Can't be actually shared, but it gives you a fighter feat. Great for those feats like power attack and the like. At later levels, even brutal strike and similar feats may be attained if your familiar meets the requirements.

Items

Weapons:

Weapons can be used by some familiars that are proficient with them, such as outsiders. Interesting weapons would include:

Spell Storing DMG: Spell storing weapons just give another way for your familiar to save actions for you.
Dispelling, Greater MIC: Well it's greater dispel magic 3/day at a great caster level. More charges from your familiar.
Illuminating MIC: Cheap and if your familiar flies, it can act as a cute little torch.
Precise MIC: Gives you the benefits of the precise shot feat. Nice for archer familiars.
Shattermantle MIC: Great! Your familiar attacks some times your enemy to reduce his spell resistance and then you blast away.
Sizing MIC: Familiars are generally not of their master's size. So with the sizing enhancement, which is cheap and has other wonderful abilities, you can trade weapons easily.

Miscellaneous:

Circlet of Persuation DMG: +3 to UMD and charisma based checks.
Glove of Storing DMG: Nice for snooping familiars, you can get it to steal stuff and store them there so it can carry them.
Ring of Spell Storing DMG: Put some spells inside it for your familiar to use.
Tomes and Manuals DMG: If your familiar can read (or with comprehend languages) it will be able to read this books to boost its stats. Mind you, i don't suggest that you should spend a +5 tome on your familiar, but more of using +1 tomes to round up stats.

Should i trade my familiar?

Well the short answer is no. Familiars are too good to trade for any other alternative class ability. Remember that even normal familiars grant you bonuses to different areas. If you consider that they use your base attack, base saves and skills, they are a weak copy (only regarding HP) of you. On the other hand, the major alternative class features that let you trade for a familiar, are the sorcerers' metamagic specialist and the wizards' immediate magic. Metamagic specialist's granted power can be easily acquired with just one feat. Immediate magic requires you to be a specialist wizard and the best ability is that of the conjuration school.

What is a familiar worth?

It's a good question. What help and bonuses can a familiar provide his master? There is a feat, called Savvy Rogue. This augments a rogue's special abilities. If you have the skill mastery special ability, this allows you to take "12" with your mastered skills. Now familiars may not have anything to do with this feat, but they, too, grant their masters +2 on every class skill they have with a score of 9 and higher. The same goes for every skill the familiar has with a score of 9 or higher. This is because a familiar can aid you whenever you make a check. Also all familiars grant a feat, alertness and maybe even more in case of improved familiars. So to sum them all up you get:

+2 to all your high skills and high familiar skills.
alertness feat.
speak with animals.
deliver touch spells. In case your dexterity lacks, just select a familiar with high dexterity.
Scry 1/day.
Your personal scout/stalker.
Additional body slots. Items such as the commander shield/armor ability provide diplomacy and will save bonuses. Same goes for a banner of the storm's eye and similar items.
Additional actions. A spell cast from a ring of spell storing or a similar ioun stone casted pre-combat inside it by you, is completely the same with your spell only you don't have to spend an action to cast it.
Extended role playing possibilities.

The list goes on and would be enormous if the improved familiars get into discussion. 

Improved Familiars

Here's a list with the various familiars you can gain through the improved familiar spells and the like. For simplicity i am going to sort them by the caster level requirement. I'll indicate the alignment of each record and the classes that will benefit most from it.

Legend: Entry Name (requirement 1)(requirement 2)(Books that appears in)

Caster Level 3:

Krenshar (+3 BAB)(N) CW: Not many movement modes or skills, but it's nice if you are going for combat because it has multiattack. The best thing about this familiar is that it has both scent and track. If you don't mind spending some ranks in survival, you can be the party's tracker!
Worg (+3 BAB)(NE) CW: As above, but better tracker. Also the trip attack is nice. Medium sized so small creatures can use this as a mount. Its ability scores are very nice and they may be able to even speak common (so they can be used to operate wands).
Celestial Template (Good) DMG/PlH/BoED: This isn't worth it a feat for a template. The magical beast type isn't going to benefit your familiar, except maybe from darkvision, but many already have it. Most familiars have 1-3 HD. So all your familiar gets is: Darkvision, resistance to Acid, Cold, Electricity, smite evil. Which is worthless since animal have crappy charisma scores and familiars don't progress HD.
Fiendish Template (Evil) DMG/PlH: Same with Celestial template.
Lizard, Spitting Crawler (Neutral) FRCS: Worthless. Why get a feat for this when normal familiars are better?
Snake, Flying (Neutral) RoF: As above.
Snake, Glacier (Neutral) SK: This is nice. Great stats and feats, medium size, fast healing and some skills.
Snake, Tree Python (CE) SK: Hides easily but there are better choices, even at this level.
Whipsnake (Neutral) SK: As above.

Caster Level 5:

Blink Dog (+5)(LG) CW: Not very nice stats and skills aren't impressive. It has however 3 feats, including track with some ranks in survival and scent. It's not good as a combat familiar, but it is great for delivering touch spells, thus it is perfect for wizards and sorcerers. The best way to use it, is by invoking hit and run tactics. Buff it up pre combat, cast a touch spell and then send it to deliver it. After delivering the spell have it dimension door back to you.
Hell Hound (+5)(LE) CW: That's a great familiar. Several fire-related abilities that aren't impressive and average stats, but fire immunity, darkvision, scent along with track and great skills. Can hide/move silently pretty easily and achieves a +15 to survival if tracking by scent, which is superb.
Shock Lizard (N) DMG: Some nice movement modes, but bad stats and skills aren't impressive.
Stirge (N) DMG: Not worth the feat. Nice if available as a normal familiar, but not otherwise.
Air Elemental (Air/Neutral) DMG/PlH: Great option. Perfect fly speed of 100ft. Darkvision out to 60 feet. Immunity to poison, sleep effects, paralysis, and stunning. Not subject to critical hits or flanking. Elementals do not eat, sleep, or breathe. Great feats (Flyby Attack, Improved Initiative, Weapon Finesse) that synergies with its high dexterity. Air mastery. Speaks, which means that it can use wands. Whirlwind and skills are worthless though.
Earth Elemental (Earth/Neutral) DMG/PlH: Same with air elemental, but a little bit worse. Maybe it has the best strength rating of all familiars, and power attack. Nice for a hexblade because it will essentially double the penalties you will apply to enemies. Also speaks.
Fire Elemental (Fire/Neutral) DMG/PlH: This is a bad elemental. But skills and attributes and not great feats. Bad movement modes.
Water Elemental (Water/Neutral) DMG/PlH: Power attack makes it very interesting. It is equal to the earth elemental and depend on the campaign environment. Also speaks.
Anarchic Template (Chaotic) PlH: This is actually ok. Gives immunities and resistances to pretty all elements, even sonic. At least it's not trash as the celestial/fiendish templates.
Axiomatic Template (Lawful) PlH: This is a bad template and doesn't worth a feat, unless you and your familiar are of the same kind, which is unlikely.
Jaculi (CE) SK: Wow, this is a 6HD familiar! Nice movement modes, great stats, great skills and feats. An ok grapple check and constrict/improved grab. Scent but no track, chameleon power which is great, spring and flying gore.
Mlarraun (Neutral) SK: Too average. Nothing interesting or hot.
Muckdweller (LE) SK: Why would you want to spent a feat to this worthless familiar?
Tressym (NG) PGtF: Again, average.

Caster Level 7:

Hippogriff (+7)(N) CW: It's large and it has a nice fly speed. Also nice stats and feats. But that's it.
Howler (+7)(NE) CW: Great stats and large. Nice hiding and scouting skills. Unfortunately no tracking ability. The quills special ability is actually quite nice and helps debuff targets.
Winter Wolf (+7)(NE) CW: Great stats, large, nice tracker if you spend some ranks in survival, immunity to cold and visions, nice feats. Speak two languages so it can make use of wands, trips with a +8 (!) bonus and its special abilities are nice.
Formian Worker (LN) DMG: It's just bad unless you want a familiar to craft stuff. It doesn't even speak.
Imp (LE) DMG/PlH: Wow. This is a powerhouse for combat familiars. Great skills, fast healing, immunities/resistances, damage reduction and alternate form which is polymorph at will. Also dodge and weapon finesse. Physical ability scores don't matter much since you will be polymorphing. Has several spells including invisibility at will. Also suggestion 1/day and commune 1/week. On top of all that it has a perfect fly speed and it speaks, so it can use wands.
Pseudodragon (NG) DMG: Nice hide check, but it isn't much. Has blindsense, SR and telepathy. Blindsense and the alternate visions help deliver touch spells, however he is tiny, so he probably need to enter the opponent's square. One of the best parts is that it is of the dragon type, which benefits alter self.
Quasit (CE) DMG/PlH: Same with imp, but worse ability scores and skills. Same power though. It's a matter of choice, really.
Homunculus (Undead) DMG: Great familiar due to immunities. However it needs the expenditure of three feats (craft arms/armor, craft wondrous and craft construct). However it's the only familiar that you can invest HD in and advance it. That means more skill points and feats. However remember that homunculi cannot speak
Lantern Archon (LG) PlH/BoED: Nice immunities and resistances but skills and abilities aren't impressive. However it's quite the party buffer: Magic circle against evil and at will abilities such as aid, detect evil and the great continual fire due to the expensive material component, at caster level 3 even. The light rays are nice because they bypass damage reduction automatically and have a nice range. Fly speed of 60ft, perfect. Teleport at will is nice also and tongues can get them using wands if they can wield them.
Mephit (Neutral) DMG/PlH/CS: Mephits have great skills and movement speeds. Also the spell like abilities they have are spamable, which is a very nice thing. Essentially you trade a feat for some extra spells/day along with other cool features. They can speak and also their charisma is great and is the key ability of UMD. Due to their higher skills, they can scout and hide, as well as bluff just a little. Damage reduction and fast healing help in battle.
Air/Ice/Dust Mephit MM: Not so hot. It has some nice skills, but stats, feats and spell like abilities are not so much.
Earth/Salt Mephit MM: Now these are worth it! They get power attack and toughness. Consult with your DM if toughness adds hit points to your familiar's HP total. Earth mephits get change size 1/hour, which gives it even more strength, making them superior for fighting classes, such as Hexblades and Duskblades. Salt mephits give even greater versatility, being able to cast glitterdust 1/hour.
Fire/Magma Mephit MM: These are the worst of the mephits. You are far better off with the other choices.
Ooze/Water Mephit: Nice mephits for water based campaign settings. They have a swim speed, which gives them huge bonuses and skill mastery to swim. They get power attack and melf's acid arrow 1/hour. Stinking cloud 1/day is nice, but it requires a saving throw.
Glass Mephit: Great feats! Power attack and Improved Initiative help in battle better. Stats and blur 1/hour helps more to fit that role.
Sulfur Mephit: A variation of the above, but a little worse. Stats don't help much. The dodge/power attack feat selection is fine though. However the spell like ability isn't that great.
Coure Eladrin (CG) BoED: This is one of the best alternative familiars. Nice movement modes. Great stats, skills, weapon finesse. Great spell like abilities, an alternate form, magic circle against evil, immunities and resistances and tongues. Cute also.
Musteval Guardinal (NG) BoED: Another great familiar. Nice resistances and immunities. Has darkvision and low light vision. Can lay on hands an amount of damage equal to their full normal hit points. A speak with animals special ability, burrow speed, nice stats, weapon finesse and quite the skill monkey.
Beguiler SS: This has true sight permanent ability. Wonderful little creature that possesses the multiattack feat, along with weapon finesse, which when buffed can prove a real menace. Nice stats and speech. Great hide skill when dry. Can wield weapons with their tail.

Caster Level 9:

Snake, Deathfang (NE) RoF: Nothing great or die for, but it does have nice skills, it's undead, the feats are ok and it does automatically bestows negative levels.

Dragon Familiars

Dragon familiars are acquired through the Dragon Familiar Dragonomicon feat. What is great about dragons, even those located in the MM, is that their racial hit dice offer some of the best abilities:[/b] full base attack bonus, 6+int skill points, 12-sided hit die and all -good saves. In addition darkvision 120ft and low-light vision out to 60ft, immunity to magic sleep and paralysis, proficient with natural weapons and when in humanoid form proficient with all simple weapons. All dragons speak draconic, so they can use wands and have blindsense out to 60ft. About skills, dragons have listen, search, spot, concentration, diplomacy, escape artist, intimidate, knowledge (any), sense motive and use magic device as class skills. Moreover some dragon varieties have their own class skills. Given that most dragons are intelligent, your dragon will easily max 5-6 skills.
Below are presented the dragons available from the Monster Manual:

Black Dragon (N, NE, CE)(7 CL): Average scores and tiny size. Can breathe underwater and has both a fly and a swim speed. Also black dragons have hide, move silently and swim as class skills, making them nice scouts. They have four hit dice only though, which gives them only two feats to spent.
Blue Dragon (LN, LE, NE)(10 CL): Again average scores, but the burrow speed is nice in conjunction with the fly speed. Six dragon hit dice are impressive, giving your familiar three feats and quite a number of skill points. In addition bluff, hide and spellcraft are class skills for blue dragons.
Green Dragon (N, LE, NE)(9 CL): As with black dragons, but better. Instead of swim as a class skill, these dragons favor bluff, which may result in interesting social encounters.
Red Dragon (CN, CE, NE)(12 CL): Wow these get seven dragon hit dice at wyrmling age and are medium. Their physical attributes are great, but they only have a fly speed. Their additional class skills are appraise, bluff and jump, not exactly impressive.
White Dragon (N, CN, CE)(7 CL): This is the dragon you will be getting most easily, but i don't think that it's worth it. They have really ugly mental attributes, but their movement modes are great. A small bonus is the icewalking ability, but it's pretty limited.
Brass Dragon (NG, CG, CN)(9 CL): Some nice movement modes, but only four hit dice and average ability scores. What is nice about brass dragons is their skills: bluff, gather information and survival. They are able to pick the track PHB feat and/or the Urban Tracking RoD and track for you. They can also use speak with animals at will.
Bronze Dragon (LG, LN, N)(11 CL): Six hit dice and disguise, swim and survival as class skills. They can too speak with animals at will and track for you if needed. Their mental ability scores are great.
Copper Dragon (CG, N, CN)(10 CL): While they have five hit dice, they are not impressive at all. Little movement modes, tiny size, average scores and bluff, hide and jump as class skills. Spider climp is nice though.
Gold Dragon (LG, NG, LN)(14 CL): Wow. Eight dragon hit dice, great scores and medium size. Great fly speed and an alternate form polymorph-like ability three times per day. Skills are not impressive, as they get disguise, heal and swim, but they have applications.
Silver Dragon (LG, NG, N)(12 CL): Just a little behind of the gold variety, comes the silver. Their physical attributes are average, but mental are the same. Their movement modes though lack. Alternate form is very nice and cloudwalking, the ability to treat clouds as solid ground, is the icing on the cake. Their class skills are bluff, disguise and jump, not that impressive.