Elgg is open source software to create a social networking website -- like Facebook or MySpace.

It can be downloaded and installed on any web server, meaning that we can create social networks for our own organizations -- and not rely on hosted services we do not own or control (including Ning).

Elgg is currently in version 1.x and at the time of UnionBook's launch, we were using the very latest version of the software.  The largest installation of Elgg currently has over 50,000 participants, so we know that this is tried and tested software -- even if we stumble on the occasional bug.