Open Atrium
Open Atrium looks interesting: a “team portal starter package” that’s designed to be extensible and customizable, allowing end-users to built their own modules, change and re-skin the app, and tweak the workflow.
The built-in set of features is impressive, including a blogging engine and iCal sharing. Also worth noting, the source code is GPL 2b, built on top of Drupal.
(via Girl Friday)