Each day there's a new website that will allow you to login with your Facebook account rather than logging into the site directly. For example, instead of logging in to Flickr through your Yahoo ID, simply put in your Facebook account login instead.
According to Edison Research, approximately 51% of Americans are now using the social networking site. With so many people using it to connect with others it should only be a matter of time that classrooms will need to use it to connect with the world outside of the four classroom walls.
For resources, please see: 100 Ways You Should Be Using Facebook In The Classroom