Invision Community - Invision Community is a flexible, integrated set of apps for building communities on the web.
SocialEngine - Socialengine PHP: Elevating Your Online Community Experience.
XenForo - Intuitive. Social. Engaging. Fast. XenForo brings a fresh outlook to forum software.
mooSocial - mooSocial is the best social network script to create a niche community or social site.
Mobilize - Mobilize is a scalable messaging app built for large groups.
JomSocial - Open Source Social Networking Software. Award winning open source community software by JomSocial. This social networking software is widely used by many Joomla users.