eXo Platform - Digital workplace solution
Trello - Infinitely flexible. Incredibly easy to use. Great mobile apps. It's free. Trello keeps track of everything, from the big picture to the minute details.
Basecamp - A simple and elegant project management system.
Notion - All-in-one workspace. One tool for your whole team. Write, plan, and get organized.
BuddyPress - WordPress social networking in a box.
Slack - A messaging app for teams who see through the Earth!