Alright, we already have:
Adept (Dungeon Master's Guide)
Aristocrat (Dungeon Master's Guide)
Barbarian (Player's Handbook)
Bard (Player's Handbook)
Basiran Dancer (Kenzer's Kalamar Player's Guide)
Brigand (Kenzer's Kalamar Player's Guide)
Cleric (Player's Handbook)
Commoner (Dungeon Master's Guide)
Courtier (AEG's Rokugan)
Druid (Player's Handbook)
Expert (Dungeon Master's Guide)
Fighter (Player's Handbook)
Gladiator (Kenzer's Kalamar Player's Guide)
Infiltrator (Kenzer's Kalamar Player's Guide)
Inkyo (AEG's Rokugan)
Mechanist (FFG's Starfarer's Handbook)
Monk (Player's Handbook)
Ninja (AEG's Rokugan)
Paladin (Player's Handbook)
Pilot (FFG's Starfarer's Handbook)
Psionics Handbookon (Psionics Handbook)
Psychic Warrior (Psionics Handbook)
Ranger (Player's Handbook)
Rogue (Player's Handbook)
Samurai (Oriental Adventures)
Shaman (Oriental Adventures)
Shaman-bis (Kenzer's Kalamar Player's Guide)
Shugenja (Oriental Adventures)
Sohei (Oriental Adventures)
Sorcerer (Player's Handbook)
Spellsinger (Kenzer's Kalamar Player's Guide)
Warrior (Dungeon Master's Guide)
Wizard (Player's Handbook)
Wu Jen (Oriental Adventures)
And I havn't listed unofficial NPC classes (thug, sailor, etc.), nor any class from not-so-D&D d20 sources like Wheel of Time.