The good guys at Development Seed rolled out a rather hotly anticipated product this afternoon known as Open Atrium.
The web based intranet platform including several built in common features such as groups, projects, case tracker, per-user blogging facilities and a rather useless shoutbox facility.
Development Seed have pulled together a lot of strong Drupal components to provide some great functionality in a really quite flexible architecture. On top of the off the shelf modules such as Views and CCK, and some home grown Development Seed releases such is as Spaces and Contexts.