I like to listen to the music that my main characters' listen to while I'm writing; I've made some stations at Pandora.com to listen to while I'm writing. One of my MC's is into Tool and I've gotten a lot of initial inspiration from Maynard, the music, and lyrics alone. It actually helped me understand my character who was strange to begin with.
My other series has a heavy metal undertone to it, so I'll listen to stuff like Megadeth, Pantera, and of course my main characters’ (who are succubus twin sisters) favorite, Metallica. Occasionally they'll get into a heated argument about pre and post Black Album Metallica and take my word for it, it’s funny.