Elgg – Open Source Social Networking & Social Publishing Platform
http://elgg.org/

Elgg, started in 2004, is an open source social engine which powers all kinds of social environments – from education to business and sports such as rugby. If you are looking to create your own social application or want to build and run a site for your organisation, Elgg is a great choice as it provides the building blocks you will need. This has been added to the tools section of Research Resources Subject Tracer™ Information Blog. This has been added to Social Informatics Subject Tracer™ Information Blog.