A buddy of mine brought this website to my attention. You can basically create your own personal radio station/playlist with a few clicks. It can either be artist based, or genre based. Overall this thing is pretty cool, and the price is right (free). It's got a huge database of bands to draw from as well .. basically anything you can throw at it .. it's got.
http://www.slacker.com/
http://www.slacker.com/