Social Networking on Last.fm

I recently signed up for Last.fm, an internet radio and music community website. Although I've only been a member for a week or so, I feel that I've been there for ages - I'm completely addicted. When you register you download the 'scrobbler' plug-in which builds your profile based on your listening preferences. Essentially it imports your music library from your music player (iTunes in my case), provides you with various statistics, snapshots of your music etc and then recommends music similar to your own. Among other things, it recommends other user music libraries, provides details of band tours, detailed discographies, as well as some free mp3s.
Some artists that I have discovered as a result include Roy Harper, Amadou and Mariam (from Mali), and Brett Dennen. I also discovered how much I've played music by Richard Thompson, a slightly scary statistic!
Last.fm started in 2002, but was purchased by CBS in 2007. It claims to have over 21 million users across the globe.
Check it out, it's free, although premium subscription is $3 per month. It's a cool website and if you're into social networking then you'll get as much out of it as you're prepared to put in.
Oh, and if you're wondering who Amadou and Mariam are, here's a video of them on the Jools Holland show in 2005: