Google Groups - Google Groups allows you to create and participate in online forums and email-based groups with a rich experience for community conversations.
Vanilla Forums - Build an engaging community forum using Vanilla's modern cloud forum software.
TidyHQ - Organization management tool to support membership, subscriptions, event planning, and outreach.
Forumbee - Forumbee offers community forums for discussions, feedback and Q&A.
Nabble - Nabble is a forum software that are embeddable and fully customizable with scripting language.
Discourse - Discourse is an open source discussion platform built for the next decade of the Internet.