If you are a music lover, then you need to try Pandora. It is a streaming audio site that asks for some music you like and then finds similar music.
This is far more than just a “similar genre” or “other people who liked this” kind of thing. They have actually built a mammoth database of the characteristics of songs, so based on what you like, it looks for songs with similar characteristics. As new songs are introduced you rate them. It has definitely thrown a few surprise songs my way that I quickly skipped (can you say Backstreet Boys?), but I’ve also found some new bands that have piqued my interest.
I also have to give it a big thumbs up for letting you try it out without registering. I’m not sure I would have bothered had that been the case. Why can’t more sites figure that out?