City of Brass
Pathfinder (still waiting on this) Expedition to the Ruins of Greyhawk
Examplars of Evil
Grand History of the Realms Monte Cook's World of Darkness
Pathfinder
Gamemastery stuff (maps, modules, maybe some of those steel spell templates)
Monster Ecologies
Dungeon Tiles IV: Ruins of the Wild
Drow of the Underdark
Complete Champion
Expedition to Undermountain
Monster Manual V
Expedition to the Ruins of Greyhawk
City of Brass
Rules Compendium
Dungeon Survival Guide
Dungeon Tiles V: Lost Caverns of the Underdark
Elder Evils
Tegel Manor
World on Fire (for Spycraft) - I'll admit though I am pretty handy with fantasy and SF world design, I often find myself at a bit of a loss for spinning my own modern setting elements. Shadowforce Archer was a bit too out there for me taken as a whole, but World on Fire looks like it will scratch the right itch.
Empire of the Ghouls (Wolfgang Baur's next open design project) - I'm an old Clark Ashton Smith fan and it looks like this is an adventure that could bring the creepy villainous ghouls to life.