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.
MS SharePoint - Share, organize, and discover information with Microsoft SharePoint. Learn about SharePoint Online, OneDrive for Business, and Apps for SharePoint
Notion - All-in-one workspace. One tool for your whole team. Write, plan, and get organized.
NemakiWare - NemakiWare is an Open Source CMIS-compliant platform for document management.
Slack - A messaging app for teams who see through the Earth!
Mayan EDMS - Document management without the headaches.