Question has been asked on some mailing lists recently, but I'm curious as to what music/thing (if at all) do you listen to while developing? As I'm asking the question, I'll give the first reply: nothing.
Years ago, I used to listen to a variety of things, including Phantom of the Opera, Guns'n'Roses, Pearl Jam, Pink Floyd, Pink Floyd, Pink Floyd, Roger Waters and some early Pink Floyd. For the past couple of years however, unless I'm doing mechanical coding, I don't listen to music, or anything for that matter. I find, especially when I'm thinking about design, that it distracts me. I've even tried music with no lyrics (except Kenny G.)
Maybe I'm just getting old...