Although I have a dislike of almost all "social" network sites, I've decided to sign up with Friendfeed. Friendfeed is an agregator, that imports data from all the major networks like Facebook, Last.FM, Twitter and pretty much anything that exports an RSS feed (like this blog).
The idea is that you can give your friends a single URL to track you, instead of having to follow all those individual services.

To me Friendfeed is just a fancy bookmark-editor. There are so many services that keeping track of all those accounts, let alone updating them quickly becomes an impossible task.
At Friendfeed I get a long list of the most popular services on the internet, I'm subscribed to most of them, but half of the time I never return after the first visit. This way I'm atleast reminded that I have an account.

In case anybode cares, my feed is at: http://friendfeed.com/capslock2000