Google Groups - Google Groups allows you to create and participate in online forums and email-based groups with a rich experience for community conversations.
Groups.io - Email and web based discussion group software, includes archiving, emails, wiki, polls, file...
TidyHQ - Organization management tool to support membership, subscriptions, event planning, and outreach.
Gaggle Mail - Gaggle Mail is a simple and easy to use email list manager.
Mighty Networks - Mighty Networks enables entrepreneurs, organizations, and companies to create and grow a community-powered brand.
Mailman - Mailman is free software for managing electronic mail discussion and e-newsletter lists.