In short: I made a Pandora station for programming and I've been tweaking it since 2009.
There's a certain kind of music that I like to listen to while I'm writing code. It's mostly instrumental, fairly mellow (but not too mellow), and with a steady beat. Most importantly, it's not distracting.
I've been tweaking a Pandora station called "Programming" since February of 2009, and I must say that I'm pretty happy with it. If you'd like to give it a try, go and give it a listen.
I hope you enjoy!