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.
Gather Town - Spatial video-chat worlds for work and play
Mailman - Mailman is free software for managing electronic mail discussion and e-newsletter lists.
Nicebreak - Virtual events for your team that they will love
Sympa - Sympa is an open source (GNU GPL) mailing list management (MLM) software.
HyHyve - Online networking with real-life interactions
MailChimp - MailChimp is the best way to design, send, and share email newsletters.