draw.io - Online diagramming application
Xmind - Xmind is a brainstorming and mind mapping application.
LucidChart - LucidChart is the missing link in online productivity suites. LucidChart allows users to create, collaborate on, and publish attractive flowcharts and other diagrams from a web browser.
MindNode - Delightful Mind Mapping for your Mac, iPad and iPhone. MacCapture Your Thoughts. Any idea starts with a loose collection of .
PlantUML - PlantUML is an open-source tool that uses simple textual descriptions to draw UML diagrams.
MindManager - With MindManager, flexible mind maps promote freeform thinking and quick organization of ideas, so creativity and productivity can live in harmony.