To take part in the beta, go to the Settings screen from the File menu while logged into Steam, and click the "Change..." button in the "Beta participation" area. Restarting Steam will enable the new Community tab, from which you may manage your profile, friends list, events, and groups. My current Steam Rating is "0 - Teh Suck."

Viewing friends' profiles or group profiles allows you to monitor the gaming activity of friends or group members, as well as participate in text and voice chat rooms. Non-Steam games can be added to the Steam list from the Games menu. If a friend is playing a game, you can launch that game through a context-sensitive menu or, apparently, join that friend's game if applicable.