Excalidraw

Includes document creation and sharing, e-mail, instant messaging, audio/video calling, online meetings, ...

The de facto online diagramming tool which allows you to visually communicate, collaborate, and share ideas.

Work together with an unlimited number of others to create and edit diagrams in real time.

A time management SaaS used by major companies such as Pepsi, H&R Block and Panera.

An open source web based collaboration platform which allows businesses to manage project tasks, billing, ...