I have a large selection of mp3s ripped from my CDs.
I just let the server send them to me randomly, which can be wierd with Siouxsie, Ministry, Kate Bush, NIN, Ramones, Jim Carrol, Liz Phair, Animals, and many others.
I'll listen to the first few songs, but then I'll zone out and just code. The only thing that will break me out is if something I don't like sneaks in.