GNU Mailman is a mailing list management software. Mailman project was started long time ago before the Millennium. Since its birth it has become the most intelligent tool for handling mailing lists ever. Huge number of companies with Fortune 500 members among them have been using Mailman for years. The new version Mailman 3 brings to us even better user experience and communication power.
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
Sympa - Sympa is an open source (GNU GPL) mailing list management (MLM) software.
Bylde - Bylde is a SaaS platform you can use to Start, Manage and Grow your groups and communities.
MailChimp - MailChimp is the best way to design, send, and share email newsletters.