Pandora.com allows you to type in any band, song, or genre of music and Pandora will play a bunch of songs with similar feal and sound. If you sign up with them, you can save all the "stations" that you create with your favorite music.

Although this site is great, it has definitely gone down hill since the start. Now there are constantly ads playing in between the music, and giant obstructive lay-outs that advertise one thing...

My personal "Usefulness meter?" About 60%