Friendfeed tracks your friends

FriendFeed, which makes it easy to keep track of your friends' web pages, videos, music, pictures and more on the Internet, is currently in private beta.

For example, keep track of your friends' blog updates, what new videos they're bookkeeping on Youtube, what Twitter is saying, what new pages they're sharing on StumbleUpon, what songs they're listening to on LastFM, and so on :).