Compiled Familiars Table

Familiar Special
Armadillo Master gains +1 natural armor bonus to AC.
Badger Master gains +2 to escape artist checks
Barracuda Master gains +1 to Reflex saves
Bat Master gains +2 to listen checks
Beaver Master gains +2 to swim checks.
Bird, Other Varies
Bobcat Master gains +2 to move silently checks
Cat Master gains +2 to move silently checks
Chipmunk Master gains +2 to Hide checks
Crab Master gains +1 natural armor bonus to AC.
Crow Can speak one language
Chameleon  Master gains +2 to Hide checks
Dog Master gains +2 to Sense Motive checks
Eagle Master gains +2 to Spot checks.
Eel Caster gains +2 to swim and escape artist checks.
Exotic animal varies
Falcon Master gains +2 to Spot Checks.
Ferret Master gains +2 modifier on Reflex saves
Fish, small Master gains +2 to swim checks
Fox  Master gains +2 to Reflex saves
Frog Master gains +2 on Jump checks
Hare Master gains +2 to Listen checks
Hawk Master gains +2 to Spot checks
Hedgehog Master gains +1 natural armour class bonus
Lizard Master gains +2 to climb checks
Lobster Master gains +1 natural armor bonus to AC.
Mole Master gains +2 to listen checks
Monkey Master gains +2 to climb checks
Mouse Master gains +2 to Move Silent checks
Octopus  Master gains +2 to Hide checks while underwater and +2 to Swim checks
Opossum Master gains +2 to climb checks
Otter Master gains +2 to swim checks
Owl Master gains +2 to move silent checks
Parrot  Has +2 Intelligence; speaks one language
Porcupine Master gains +2 to intimidate checks.
Rabbit Master gains +2 to jump checks
Raven speaks one language
Raccoon  Master gains +2 to pick pocket checks
Rat Master gains +2 to Hide checks
Scorpion Master is immune to his familiar's venom
Seahorse Master gains +2 to swim checks
Shrew Poisonous bite
Slug  Master gains 1/- damage reduction
Skunk The master is immune to his familiars "musk attack"
Snake, small constrictor Master gains +2 to escape artist checks
Snake, tiny venomous The master is immune to his familiar's venom.
Spider, poisonous Master gains +2 to fort saves vs. natural poisons
Squirrel  Master gains +2 to Climb checks
Stingray Master gains +2 to Fort. saves vs. natural poisons
Tarantula  Master gains 2 points of fire resistance (as a weaker version of endure elements)
Thrush Speaks one language
Toad Master gains +2 to constitution score
Turtle  Master gains +2 natural armor bonus to AC
Weasel Master gains +2 to reflex saves
Vulture Master gains +4 to Fortitude saves versus disease

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Armadillo - These familiars are only available in appropriate climates/terrain (arid grasslands and steppe-like regions).

Badger - Hot-tempered animals, badgers can make for dangerous familiars if not treated very, very well.

Bat - These night time flyers are an usual familiar choice.  They use a sonar based system for aiding in navigation when flying at night.  (See PHB addendum for stat-block)

Beaver -

Bird, Other.  This category is the catch-all for all birds not covered specifically already, the DM is encouraged to arbitrate any master 'bonuses' if any on a case-by-case basis.

Cat - Most people either adore them, or hate them, but no one can contest that a cat makes for a fiery and independent pet and familiar. (See PHB addendum for stat-block)

Chameleon - This sluggish insectivorous lizard has independently mobile eyes and can change colors to blend in with its background.

Dog -  An excellent familiar as well as man's best friend, a dog familiar is of the small dog variety, such as terrier.  Dog statistics are in the MM.

Eagle - A proud and capable familiar indeed.  (See MM stat-block)

Eel - As with the Octopus, this familiar is really only suitable to an aquatic dwelling spell-cater.

Exotic animal - Spellcasters who summon their familiar in an unusual or remote location may have the option of choosing more exotic animals as familiars. Consult with your DM for possible options.

Ferret - Cute, loveable, and incredibly mischievous.  Ferrets make wonderfully affectionate familiars.

Frog - Almost as unusual a choice in familiars as toads, Frogs also have the downside of being amphibians which typically need regular exposure to water to avoid 'drying out.'

Fox - This beautiful small canine is quick-witted and swift. Varieties include the slightly larger gray fox, the red fox, and the white Arctic fox. (see dragon #280 for stat-block)

Hare - This larger cousin of the rabbit tends to be skittish, but hare familiars are much more brave.  They have excellent senses of smell and hearing, and are swift runners and talented jumpers. (see dragon #280 for stat-block)

Hawk - This category of familiars includes falcons as well.  A proud and capable familiar indeed.  (See PHB addendum for stat-block)

Hedgehog - An unusual choice in familiar, the hedgehog is an adorable creature.

Lizard - A wide variety of small lizards make excellent familiars.  Geckos, iguanas, and similar creatures. (see dragon #280).

Monkey - Monkey familiars are unavailable to most arcane casters, as they are not native to a typical 'European-style' setting, but for those who have the ability to get a monkey familiar, they are an excellent choice.  This category of familiar presumes monkeys which are no bigger than a housecat, such as colobus or capuchin monkeys. (see MM for stat-block)

Mouse - Perhaps the smallest and most innocuous of the familiars listed here, a mouse is able to go almost anywhere unseen.  (see dragon #280 for stat-block)

Octopus - This remarkably intelligent cephalopod mollusk is an ambush hunter that can change colors to blend in with its background. Although normally restricted to salt water, the octopus can live for several minutes out of water, climbing and moving swiftly on its eight tentacles. Lacking bones or hard parts other than its beak, the octopus can squeeze through very small openings.

Otter -  Otters are clever, excellent at swimming and diving, and have paws with great dexterity.  (see dragon #280 for stat-block)

Owl - Silent and deadly hunters of the night?  Not all owls are nocturnal, though most are.  This category of familiar is perfect for nocturnal spell-casters.  (See PHB addendum for stat-block)

Parrot - This brilliantly-colored, long-lived, nut- and fruit-eating bird can speak intelligently. Parrots prefer warmer climes. They are often raucous and noisy, even in inappropriate circumstances.

Porcupine -

Raccoon - These clever omnivores have highly dexterous hands capable of a wide variety of manipulations. They have mischievous spirits, especially when it comes to food supplies.  (see dragon #280 for stat-block)

Rat - (See PHB addendum for stat-block)

Raven - Annoying and vocal as they may be, Ravens make for capable familiars.  (See PHB addendum for stat-block)

Skunk - Most renown for their ability to spray an odiferous musk when angered or frightened, skunks make an unusual, though interesting, familiar choice.  (see dragon #280 for stat-block)

Slug - These large terrestrial mollusks leave a trail of slime wherever they go…very slowly. They are nearly motionless on the human scale. Some are brightly colored. Their lack of hard parts makes them very resilient to injury.

Snake, Small Constrictor - The constrictor variety of snakes deserved recognition, so I through them in.

Snake, Tiny venomous - With a mildly poisonous bite, these snakes make for an interesting familiar.  (See PHB addendum for stat-block)

Squirrel - These arboreal rodents are quite trusting. They may become sluggish in winter.  (see dragon #280 for stat-block)

Tarantula: These large, primitive spiders are ambush hunters and prefer warm, dry climates. Their pedipalps (auxiliary mouth parts) are enlarged and serve as a fifth pair of legs.

Toad - An odd choice for a  familiar, but some spell-casters prefer odd.  (See PHB addendum for stat-block)

Turtle - These represent a wide variety of armored anapsid reptiles, who are typically semi-aquatic. Purely terrestrial turtles are often called tortoises. Most can partially withdraw their heads and limbs within their protective shell; the "box turtles" can completely seal their shell.

Vulture - These carrion birds are renowned for their ugliness; most have completely bald heads and necks. Because of their taste for rotten flesh, they are nearly immune to infectious disease.

Weasel - (See PHB addendum for stat-block)

Thanks to Greg Morrow  and Dragon #280 "A Little More Familiar" (by Stephen Kenson) for the bulk of the familiar idea and concepts.