TWiki - the Open Source Wiki for the Enterprise

TWiki, a flexible, powerful, and easy to use enterprise wiki, enterprise collaboration platform and knowledge management system. It is a Structured Wiki, typically used to run a project development space, a document management system, a knowledge base, or any other groupware tool, on an intranet or on the internet. Web content can be created collaboratively by using just a browser. Users without programming skills can create web applications. Developers can extend the functionality of TWiki with Plugins. TWiki fosters information flow within an organization; lets distributed teams work together seamlessly and productively; and eliminates the one-webmaster syndrome of outdated intranet content.

http://twiki.org