We can delete our own comments ? I thought only administrators could.
Just checked, tried to violently slaughter this poor comment, that ain't allowed.
Pure Beastiaries:
WotC: Monster Manual 1 & 2, Monster Compendium: Monsters of Faerûn, the upcoming Fiend Folio.
d20: Creature Collection 1, 2 & the upcoming 3, Tome of Horrors, Monsternomicon, Minions: Fearsome Foes, Jade Dragon & Hungry Ghosts, Creatures of Rokugan, Legions of Hell, Armies of the Abyss, Monsters of Norrath, Nightmare & Dreams, Liber Bestiarus, Encyclopedia of Demons & Devils, Denizens of Darkness, Draconic Lore, the upoming Mindscape: Beasts of the Id, Races of Evernor 1, 2, 3 (in playable race format), Mythic Races (player race also), Galactic Races (yet again), Lord Erbians Stellar Bestiary (Fading Suns), Horrors of the Weird West (Deadlands)...
Rulebooks with creature content:
WotC: Psionics Handbook, Manual of the Planes, Deities & Demigods (cyclop, lesser cyclop, faun, greater mummy, minion of Set, valkyrie, einherjar) Oriental Adventures, Epic Level Handbook, Forgotten Realms Campaign Setting, Magic of Faerûn, Silver Marches, Races of Faerûn, Savage Species, Faiths & Pantheons (gondsman, zin-carla, chosen of bane), Book of Vile Darkness, Call of Chtulluh d20, Wheel of Time...
Others: Too much to list! Ravenloft, Campaign Setting, Seas of Blood, Relics & Rituals (greater mummy), most of AEG's instant adventures (1 new creature each), Thee Compleat Librum of Gar'Udok's Necromantic Artes, Galaxy Guide, Seafarer's Handbook, all Books of Eldritch/Hallowed Might, Necromancy: Beyond the Grave, Demonology: the Dark Road (Free Web Enhancement), each city book about the Scarred Lands (Mithril, Hollowfaust, etc.), Warrens of the Ratmen, about a thousand other I forget...
The Creature Catalog Locator, while not exhaustive, is a good source of reference for what you may found in what.