Facebook isn’t just a great way for you to find old friends or learn about what’s happening this weekend, it is also an incredible learning tool. Teachers can utilize Facebook for class projects, for enhancing communication, and for engaging students in a manner that might not be entirely possible in traditional classroom settings.
http://www.onlinecollege.org/2009/10/20/100-ways-you-should-be-using-facebook-in-your-classroom/