Elgg. ‘Elgg is an open source software platform designed to allow people to easily connect and share resources. Established in March 2004 by Ben Werdmuller and David Tosh, Elgg allows you to create a social network and host it on your own infrastructure, modifying the features to fit your specific needs. Users establish personal digital identities and connect with other people, collaborate with them and discover new resources through their connections.
Plugins allow users on different social networks to collaborate, and provide specific functionality for tasks like project management, mobile browsing, and collaboration through user-controlled wikis.’