I like
Last.fm a lot. It's a good way to find artists similar to ones you are already listening to, each artist has their own page and each SONG by an artist has its own page. The song pages often have a sample of the song or an embedded video of the full song. There are also "stations" where you can insert an artist or genre and it will play songs similar to them. I also like it because you can track your own listening from your iTunes/iPod as well. My profile is linked in my signature if you're curious.