GURPS Arabian Nights *OP
A sourcebook for games set in medieval Arabia. Covers both history and fantasy. Not just useful for GURPS, can be used with other rule systems.
GURPS Greece
GURPS Vikings
Star Wars RPG: Collapse of The Republic
S. Petersen's Field Guide to Lovecraftian Horrors: A Field Observer's Handbook of Preternatural Entities and Beings from Beyond the Wall of Sleep (Call of Cthulhu Roleplaying)
GURPS Time Travel (GURPS: Generic Universal Role Playing System)
Fantasy Flight Games FFG Star Wars RPG: Rise of The Separatists Hardcover