Elgg is an open source social networking system based around choice, flexibility and openness: a system that firmly places individuals at the centre of their activities.
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.
In order to achieve this, it includes customisable profiles / dashboards, blogging, RSS aggregation, podcasting facilities, full internationalisation, LDAP and more. There is a flexible plugin API - available plugins include integrations with Akismet and Amazon S3, with many more to come. There is also an authentication API, and OpenID support will be released in the first quarter of 2007.
