Zelos - A very simple app for mobile teams - tasks and chats on desktop and mobile.
Disciple - Grow, engage and monetise your community with Disciple community software. Get your own branded community platform on Web, iOS and Android
Google Groups - Google Groups allows you to create and participate in online forums and email-based groups with a rich experience for community conversations.
Proboards - ProBoards is a host of free forums with customer service.
Mailman 3 - Dedicated Mailman 3 installation. Unlimited lists/configuration. Free subdomain at mailman3.com. Dedicated support for list admins.
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!