So organizing your friends into lists on facebook is an effective way to communicate, invite, and select from groups of people that you are connected with. You can separate your friends into lists for ease of use. Want to only see updates from your High school friends, easy. How about only co-workers, super easy. Maybe organize your friends into bowling leagues or band fans. EASY.
Take a look at this video and you should get a couple ideas of just how useful this can be for you.