Mailman 3 - Dedicated Mailman 3 installation. Unlimited lists/configuration. Free subdomain at mailman3.com. Dedicated support for list admins.
Meetup - Helps groups of people with shared interests plan events and facilitates off line group meetings in various localities around the world.
Mailman - Mailman is free software for managing electronic mail discussion and e-newsletter lists.
Eventbrite - Discover Great Events or Create Your Own & Sell Tickets
Google Groups - Google Groups allows you to create and participate in online forums and email-based groups with a rich experience for community conversations.
Bigtent - BigTent is a web-based organization and communication portal for groups.