Zelos - A very simple app for mobile teams - tasks and chats on desktop and mobile.
Discourse - Discourse is an open source discussion platform built for the next decade of the Internet.
Google Groups - Google Groups allows you to create and participate in online forums and email-based groups with a rich experience for community conversations.
XenForo - Intuitive. Social. Engaging. Fast. XenForo brings a fresh outlook to forum software.
Mailman 3 - Dedicated Mailman 3 installation. Unlimited lists/configuration. Free subdomain at mailman3.com. Dedicated support for list admins.
phpBB - Raspberry Pi. The Raspberry Pi is a cheap, credit-card sized computer. The official website uses phpBB for their discussion forums. phpBB is not affiliated with nor responsible for any of the sites listed on the showcase.