Basic class breakdown.
Spellcaster:
Mage (magic), Warlock (evil magic), Druid (nature), Shaman (shamanistic magic)
Medic:
Druid (nature), Priest (holy), Palidan (holy warrior), Shaman (shamanistic magic)
Fighter:
Warrior (basic fighter), Rogue (assassin), Palidan (holy warrior), Hunter (ranged overpowered assassin with pet)
Race breakdown:
Gnomes are smart. +Intellect
Humans adjust to new stuff quickly. +to reputation gain, and for some reason, stealth detection ability.
Dwarves are greedy bastards. Ability to find treasure (lootable creatures) on minimap. They're also so damn think they can turn into chunks of stone. Hm!
Night Elves are weird. Ability to turn invisible (low-powered stealth) and some other benefit.
Trolls are smart and get pissed easy. Ability to go berzerk after getting critically hit, and faster mana regain.
Orcs pound the poop out of people. I can't remember their ability.
Undead don't breathe very much. They're dead. Additional 300% time underwater without breathing. Plus they don't get scared, so they have "Will of the Forsaken" (breaks fear)
Tauren pick flowers, and are heavy. +15 to herbalism and the ability to stun everyone for a second or so.