You guys have all heard of Pandora, right? The online "radio" site where you can type in a favorite artist or song and the site will generate an entire radio station based on that entry?
Yeah, I'm sure you have.
You may not have heard of Last.fm, though, which is very similar to Pandora. You build channels based on your favorite artists or songs, but you also have the ability to add songs and artists to playlists and write reviews and such.
It also has a better search feature than Pandora, and it's more of a "community," if will.
The best feature about Last.fm, though, is the Last.fm Firefox Add-on. You download this puppy, you put it right up on your Firefox Toolbar and before you know it you're ripping your hair out to crazy crap like Slayer and Pantera (that was my day yesterday... surprisingly it was one of my most productive days ever).
The toolbar feature is great--you don't have to open an entire tab or window to listen to your tunes.
You should give it a try. And let me know if you find any cool stations.