I signed up with Last.fm back when they were still “Audioscrobbler.” The plugin was kind of crufty, needing to be manually installed and accessed via the iTunes “Visualizer” menu, and it didn’t seem very reliable, so I gave up on it and cancelled my account. Seeing leeched Last.fm output from a bot in iEatTapes IRC (the bot could retrieve a user’s last played music) got me interested again, though, so I decided to give it another spin. It’s much improved; the plugin no longer needs to be kludged into iTunes, and has been sending music data all day.
So here’s my Last.fm user page, where you can see what I’ve been listening to. There’s a wizard to put your charts on your site via a javascript snippet, and they also provide data feeds in text and XML. At some point I might try parsing some of that into a sidebar “recent tracks” list, if you don’t mind seeing lots of medieval Latin and Italian song titles in there.