No Forgotten Realms. No Eberron. Mostly. Sometimes we harvest from those books.
Core.
PHB II
DMG II (though, not really)
MM 2-3
Complete Arcane/Mage/Divine/Warrior/Adventurer (No one's got Scoundrel)
Heroes of Horror
Libris Mortis
Tome of Magic
Magic of Incarnum
Races of Wild/Stone/Destiny/Faerun (mostly for the feats and PrCs)
Plus some other books that escape my mind at the moment.
Basically, if I get a good long read of the book, I'll allow it. Maybe.
My friend and I are the only two who actually buy books, so we usually both the books a read through before it comes into play.
PHB
DMG
M M
M M 2
M M 4
Creature Collection 2
Expanded Psionics
Complete Psionics
Complete Warrior
Complete Divine
Complete Arcane
Races of Stone
Races of Bastards and Cross-Breeds
Lords of Madness
Eberron book
Xen'drik book
Explorer's Handbook
Spell Comp.
Stormwrack
Draconomicon
and lots of use of DDM figures, other figures, Battle mats and Dungeon Tiles.
Generally speaking, all of the Eberron hardcovers and all non-Forgotten Realms WotC hardcovers are permitted in my game.
That said, there are a few elements of those books that I don't allow; conversely, there is some third-party material I'd probably allow if a player asked permission.