Mighty Networks - Mighty Networks enables entrepreneurs, organizations, and companies to create and grow a community-powered brand.
Groups.io - Email and web based discussion group software, includes archiving, emails, wiki, polls, file...
Bigtent - BigTent is a web-based organization and communication portal for groups.
Gaggle Mail - Gaggle Mail is a simple and easy to use email list manager.
Nabble - Nabble is a forum software that are embeddable and fully customizable with scripting language.
Mailman - Mailman is free software for managing electronic mail discussion and e-newsletter lists.