I added a "Music Habits" link to the navigation links in the bar to your right. This link goes to my page on Audioscrobbler. Audioscrobbler, for those who don't know, is a wicked keen site that has plugins you can download for your music player of choice (Mac, PC, Linux, whatever) and it tracks what you listen to, giving you a list of what your favorite songs, favorite artists, things like that are.
Sure, your music app probably already does that (I know iTunes does, if you use Smart Playlists), but the keen thing is, it's a community, and once you've listened to at least 100 songs with the plugin enabled, it starts matching you up with other people in the community who share your musical tastes. Not that you have to talk to them or anything if you don't want to, but it starts giving you suggestions based on their likes as well, which is a really great way to find new music that you just might love.
On top of all that, they offer a customized streaming internet radio service called Last.FM, which you can base on just your collection, or on the collections of your musical neighbors as well. Highly recommended.