Activity streams (2.0+)
Drupal Commons now provides you and your users more avenues of communication by using activity streams. By creating status messages in their own or their friends' profiles' activity streams, users can communicate with others both publicly and privately without having to explicitly create formal content.
Along with user-created status messages, Drupal Commons can display a user's activity, including content creation and group membership changes. While Drupal Commons displayed a user's activity in the past (using the Heartbeat trigger), Drupal Commons now allows for rules to be created to explicitly determine the actions you want to track.