Google Plus - Circle - A Social Network Project: The easiest way to share some things with college buddies, others with your parents and almost nothing with your boss.

The service revolves around a concept of "circles". You can create as many circles as you like, for whatever categories you want: for example family, co-workers or biking friends. Above the circles are a slew of thumbnail images of friends and contacts which Google suggests you might want in your social network. To add a person to one of your groups, drag the name into a circle. via - Reuters

Details: http://www.google.com/intl/en_uk/+/demo/