zena is a state-of-the-art CMS (content managment system) based on Ruby on Rails with a focus on usability, ease of customization and web 2.0 goodness (application like behaviour).
You can watch the videos to get a first idea.
What is OpenGoo
OpenGoo is an Open Source Web Office. It is a complete solution for every organization to create, collaborate, share and publish all its internal and external documents.