Invision Community - Invision Community is a flexible, integrated set of apps for building communities on the web.
ForumFree - ForumFree allows you to create a forum or a blog in a few simple steps.
XenForo - Intuitive. Social. Engaging. Fast. XenForo brings a fresh outlook to forum software.
Forumotion.com - Create a free forum : free forum hosting, free forum skins, templates editing, chatbox, RPG mod... Choose PhpBB 2 - 3, Invision or PunBB. Create forums now!
Mobilize - Mobilize is a scalable messaging app built for large groups.
Proboards - ProBoards is a host of free forums with customer service.