I was trying a new piece of software for my mac called 'CoverSutra' which is quite nice application. It offers a little icon of the current track being played on the desktop and has Growl support.
One of the features I didn't know much about was submission to a site called last.fm which is a music recommendation site. Coversutra will automatically upload the music you play (names of tracks only) and compare it with other people with similar listening tastes. Eventually it'll recommend local concerts and music based purely on your listening history! Sounds good to me - and it's free.
If you visit my actual website (rather than reading my newsfeed) you'll notice a little icon on the right hand side which displays my most popularly listened artists over the last week! Pretty cool - this updates live too!
Check out CoverSutra - it's only 10 euros!
Link to last.fm