I usually listen to hard stuff, like NiN or Manson while coding, but lately I've been listening exclusively to Philip Glass - Koyaanisqatsi soundtrack, Liquid Days soundtrack, his brand new Symphony #5. They're all great. I really like choral work, and most of these pieces are just "singing" - no words. There's nothing like hearing a whole choir in your headphones singing what sounds like three different parts and patterns to get the creative juices flowing!
GuildensternNegaterd character class uber alles!