I use classical conditioning on myself with genres of music to either help me focus or to relax. Basically I just always (and only) play a certain type of music when I'm working, and then switch to another type of music when I want to start winding down for the day.

I use these two stations because they have no words or commercials: (work): http://somafm.com/thetrip/ (relax): http://somafm.com/dronezone/

It definitely helps me. Sometimes if I forget to turn off the music I end up working way too late. Also, it's incredible how the focus and desire to work comes on almost instantly when I put my headphones on. I use very good passive noise cancelling headphones (they reduce ~25db of sound), so literally all I hear is the music, and I have to take them off to talk to people/leave the computer, which probably strengthens the effect