While I personally prefer electronic music, I was kind of surprised that most of the programmers I've met in person seemed to be into metal, covering pretty much everything from good old Black Sabbath through Power Metal all the way to Grindcore and Black Metal.
Not that I am judging in any way. I used to listen to a lot of Heavy Metal, and I still do occasionally (especially when I am angry/frustrated - it seems to have a cathartic effect on me).
For programming, I prefer calm, quiet, unobtrusive music, but apparently there are many programmers out there who like to rock. :)