Google Groups - Google Groups allows you to create and participate in online forums and email-based groups with a rich experience for community conversations.
Mailman 3 - Dedicated Mailman 3 installation. Unlimited lists/configuration. Free subdomain at mailman3.com. Dedicated support for list admins.
Groups.io - Email and web based discussion group software, includes archiving, emails, wiki, polls, file...
Mailman - Mailman is free software for managing electronic mail discussion and e-newsletter lists.
GroupSpaces - Free Group Website, Membership Database, Listserv Mailing List, Online Group Management Software : GroupSpaces
Meetup - Helps groups of people with shared interests plan events and facilitates off line group meetings in various localities around the world.