Quick Diagram - A tool for generating diagrams and flowcharts from text.
Xmind - Xmind is a brainstorming and mind mapping application.
draw.io - Online diagramming application
MindMeister - Create, share and collaboratively work on mind maps with MindMeister, the leading online mind mapping software. Includes apps for iPhone, iPad and Android.
Superdocu - Onboard people at scale, stay compliant.
Coggle - Coggle is a simple, beautiful, powerful way of structuring information.