a radio that "only plays music that you like"

You might've heard about this website already but I hadn't heard about it til yesterday. I looked it up this morning and used it for a few hours to supply my background music for working on homework, etc.
The website Pandora Radio is a website that is sort of like a cross between youtube and a radio. You create an account (free), and enter the name of a band, composer, or song that you like. It creates a long list of songs that have similar qualities for you, and plays them continuously, (I think) like a radio. If a song comes up that you don't like or that you've heard too many times, you can click the "thumbs down" icon on your list and it won't play it again. You can have multiple playlists.
I think its pretty cool because I get tired of listening to the same songs over and over again, and I'm not very good at discovering new songs that I like by myself. The only downside is the songs don't download, so when you want a song you have to go out and buy it.