HedgeDoc : HedgeDoc (formerly known as CodiMD) is an open-source, web-based, self-hosted, collaborative markdown editor.
You can use it to easily collaborate on ...
Zulip : Powerful slack-like open source group chat
Postal : Postal is a complete and fully featured mail server for use by websites & web servers. Think Sendgrid, Mailgun or Postmark but open source and ready f...
GitLab is a web-based Git repository manager with wiki and issue tracking features. GitLab offers hosted accounts similar to GitHub, but also allows its software to be used on third party servers.