I'm sure most people reading this have heard of the social media / music site called Last FM. I had always been meaning to check it out and finally took the plunge last week.
My favorite thing about the service is if you install a "scrobber" (I installed one with Media Monkey and its been great) literally every track you listen to is cataloged on your profile. This not only shows your friends what you've been listening to, it allows them to see charts and rankings of your favorite songs and artists. You can also integrate it with facebook, something I'm still figuring out how to use most effectively.
I was struck by how accurate my artist rankings on Last FM compare to how I would rank my favorite bands and artists in real life.
Elvis Costello, Steve Earle and Billy Bragg all have a few less plays than my bottom 4 so things switch around quite a bit. My only issue is that artists like Elvis Costello aren't grouped with "Elvis Costello and the Attractions" or "Elvis Costello and the Imposters" - if they were EC would be my 3rd favorite artist which is more accurate than just plain old Elvis Costello being #12 but #8 with the attractions. Guided By Voices may be a bit too high as well, since they have so many short songs its pretty easy to rack up a ton of plays.
I would definitely recommend last FM as a way of seeing what you're actually listening to on your PC. I guess the fact that most of its features only make since if you actually listen to a lot of music on your computer might be a turn off to some folks. Feel free to "friend" me if you use the service, I'm always interested to see what people are listening to.