I know I'm late on this but there are just too many things to do lately between my longboarding fixation and the AMC series Mad Men. Last Fm is a social music platform that allows you to share your taste in music (as you listen to it) and discover new music. You download the platform and then as you listen to your music, it scrobbles (the process of uploading the track to your last.fm profile page) the track and displays it on your profile for all to see. It even takes the play counts from iTunes and develops charts and graphs of what you listen to most.
So while on the street you may boast that your most listened to music ranges from Pavement to Radiohead, once the charts generate what you have listened to most on your iTunes, it could fall closer to Winger or Paulo Nutini. So anyway, suffice to say I love it and you should check it out as well. If you get an account be sure to let me know so we can stalk each others music tastes.