If you havn't heard of spotify, check it out, it's awesome. It's been cited by the BBC as the new napster, or bearshare or whatever the kids were using before Spotify.

Once you've downloaded the client, type in the name of a song and in less time than it takes to google it, the song is playing for free on your PC. The playback is high quality Ogg, and navigation is nice and easy.

After playing around for a bit, check out Collaborative Playlists, which authorise other users to add songs to your playlists. A friend of mine works at a radio station, so I created a playlist of my top tracks to send to him. When I sent him the link, he started listening to the tracks and within minitues had added a few of his own suggestions. The changes were updated in realtime on both copies of the playlist, so we could add songs as we chatted about them.

As an example of how playlist sharing works, here's a non collaborative playlist of mine:

Rock Monsters URI: spotify:user:joejj:playlist:3lWWsJ0KVf7yJDyPmQqOTS