For those of you looking for a good open source technology to use to improve web-based collaboration, check this piece of software out: http://sourceforge.net/projects/opensharepoint/. It is an open source clone of Microsoft's Sharepoint and visually uses the same concept. It is easy to use (checkout the demo).
For those who look for more, please checkout TIKIWIKI. InsightKnowledge Inc.'s website is build with it and provides a variety of features all targeted to improve personal knowledge managing efficiency. Feel free to contact me for a demo. I will provide a free web presentation soon.