SocialEngine – Social Network Creation Platform
http://www.socialengine.net/

SocialEngine is a PHP-based social network platform that lets you create a social network on your website. Right out of the box, your social network will offer nearly all of the features found on today’s wildly popular social networks. Unlike other social network apps, you are given absolute control over the appearance and structure of your social network. This has been added to Social Informatics Subject Tracer™ Information Blog.