Open Source Collaboration Software

Enterprise collaboration platform with over 400 extensions. Users without programming skills can create web applications. 50,000 small businesses, many Fortune 500 companies, and millions of people use TWiki, with installations of 100,000s of pages. Visit http://twiki.org/ for the open source TWiki. The TWiki community is focusing on building the best collaboration platform for the workplace. We invite you to GET INVOLVED! More at http://bit.ly/twGetInv.

Collabtive is web based collaboration software. It is an Open Source alternative for proprietary tools like Active Collab or Basecamp. Features include: Projects, Instant Messenger, Tasks, Files, Timetracking, Multilanguage, Basecamp import

Feng Office (formerly known as OpenGoo) is a free and open source online project management and collaboration tool, licensed under the Affero GPL 3 license.

Foswiki is an Enterprise wiki, typically used to run a collaboration platform, knowledge base or document management system. Users can create wiki applications using the Topic Markup Language, and developers can extend its functionality with plugins. Foswiki stands for "Free and Open Source" wiki to emphasize its commitment to Open Source software.