Elgg

Elgg is one of the first content managers to integrate services belonging to online social networks.

With Elgg you can build a website that has the following characteristics: blogging system, social network, file database, podcast, RSS, user profiles, and more.

One of the best things about Elgg is that it allows you to create communities with users and friends. The users themselves can decide who is and is not allowed to join their group.

If you don't want to activate all of its functions, the structure of Elgg can be modified to adapt to the needs of each developer.

Like other CMS, Elgg allows you to add new functions via plugins, and for personalization using themes.