I highly suggest www.last.fm to anyone with this goal. Better than pandora.com by far…it tracks what you listen to, gives you recommendations, and finds you “friends” with similar taste – so you can see what they’re listening to. I’ve found a lot of new stuff I love now on the site. And, as if that wasn’t enough, you can play full songs (and for some artists full albums) 3 times on demand for free.