First, the Facebook profile/status. You have to join Facebook in order to see everything. I have reconnected with several college and even high school friends through Facebook. They are developing an interesting revenue model as product recommendations, books, movies, etc are more meaningful from people you are already friends with than from total strangers. Facebook may become the new Google. Though I doubt Google is going anywhere!
I also added a last.fm app. This relays the last songs I listened to in my iTunes. If I'm currently listening, it updates more frequently. Like Pandora, last.fm can stream "radio" to your desktop based on your current library and listening habits, or based on the name of an artist or group you type in. CBS just bought last.fm. Evidently last.fm, more than just a social and recommending network, offers feedback to producers of the music such as when how far into a track people listened to a particular song, what they advanced to, how many times a track gets played, etc. If you're ok with that kind of information going out about your listening habits, it can be a pretty fun little tool.
Finally, I have my Digg app, which shows the latest stories I've dug. Fairly self-explanatory.