Many people who first start using Facebook often find themselves seeking out ideas for fun on Facebook. While the main page of Facebook has a very standard format with predictable sections for your "wall" and profile, there are also thousands of other ways to have a great deal of fun on Facebook.
One interesting thing to do on Facebook is searching for people you know. This search utility includes the ability to find people by their email address, people you IM with, or even people in the same networks as you (such as school or company). Best of all, Facebook uses users' profile information to suggest "people you may know."