Here we go, time for Web 2.0 Expo to start, @jonpet and @hkraft are attending a workshop called Designing Social Interfaces. The workshop is held by Christian Crumlish and Erin Malone.
Check out the design pattern wiki on the http://designingsocialinterfaces.com. A really comprehensive list on different design patterns to be used when designing websites with social networking features. The website is "a companion site to the book that Christian Crumlish and Erin Malone are currently writing for O'Reilly Media." The wiki is a really good repository with lots of different screen shots taken from various social networks.