Matt put me on to a realy cool thing, well two things really (all good things come in pairs)
The first half is a neat little pluging called audioscrobbler that drops into your favourite music player, iTunes in my case and it just hides there and sends the name of the track and the artist that you are currently listening to audioscrobbler. There is is built into a cool database of tracks that you listen to, but that is not the cool bit.
Here is where last.fm kicks in. They take the tracks you listen to and then compare them to tracks that other people have listened to and then make a custom radio station for you!
Ok so that is cool!