your own personal radio station!

Lately, I've been using Last FM. It's free to download and then you can search for the name of a band you like, or just search any old keyword really, and it will find a whole bunch of tracks by "similar" artists and play them for you, like a radio station, but without whiny disk jockeys and boring ads. It does other cool stuff too, but you should go find out for yourselves. All I know, is it hardly ever plays me a song I have to skip and it's great for when you're bored of all your playlists.