Yanni and Kenny G!
Ok, seriously, I generally use as background:
Conan the Barbarian
Lord of the Rings trilogy
Highlights from Wagner's Ring Cycle (instrumental - opera lyrics would be too distracting)
Holst: The Planets
Mussorgsky: Pictures at an Exhibition
Midnight Syndicate: Realm of Shadows, Born of the Night, or the D&D Soundtrack
The Crow Soundtrack
Batman (the Michael Keaton version) soundtrack