Sakai : An online Collaboration and Learning Environment

Sakai is an online Collaboration and Learning Environment. Many users of Sakai deploy it to support teaching and learning, ad hoc group collaboration, support for portfolios and research collaboration.

Sakai is a free and open source product that is built and maintained by the Sakai community. Sakai's development model is called "Community Source" because many of the developers creating Sakai are drawn from the "community" of organizations that have adopted and are using Sakai.

Moodle : A course management system (CMS)

Moodle is a course management system (CMS) - a free, Open Source software package designed using sound pedagogical principles, to help educators create effective online learning communities. You can download and use it on any computer you have handy (including webhosts), yet it can scale from a single-teacher site to a 50,000-student University.

eLGG: learning landscape

Elgg is an open source social platform based around choice, flexibility and openness: a system that firmly places individuals at the centre of their activities.

Your users have the freedom to incorporate all their favorite tools within one environment and showcase their content with as many or as few people as they choose, all within a social networking site that you control.

AroundMe Offers Free Software to Create Your Own MySpace

AroundMe is a free software solution for those who would like to create a collaborative web space (i.e. MySpace clone).

With this tool you can make your own website and layer in social networking components such as wikis, blogs, and forums. OpenID integration is one of the options that can be extended to the end users as well. AroundMe is released under a GPL license, is free to download, and also features a plug-in API. The hope for the creators of AroundMe is that people will use this tool to create websites for others to network around, forming groups (as with Ning) and offering up user-generated content.

Somewhat similar services include Wetpaint and Synthasite, and enterprise solutions such as MindTouch.