Invision Community - Invision Community is a flexible, integrated set of apps for building communities on the web.
Forumbee - Forumbee offers community forums for discussions, feedback and Q&A.
XenForo - Intuitive. Social. Engaging. Fast. XenForo brings a fresh outlook to forum software.
Vanilla Forums - Build an engaging community forum using Vanilla's modern cloud forum software.
Mobilize - Mobilize is a scalable messaging app built for large groups.
FUDforum - FUDforum is a free and open source Internet forum software