Vanilla Forums - Build an engaging community forum using Vanilla's modern cloud forum software.
SocialEngine - Socialengine PHP: Elevating Your Online Community Experience.
Forumbee - Forumbee offers community forums for discussions, feedback and Q&A.
mooSocial - mooSocial is the best social network script to create a niche community or social site.
Discourse - Discourse is an open source discussion platform built for the next decade of the Internet.
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.