vym - VYM (View Your Mind) is a tool to generate and manipulate maps which show your thoughts.
UX Flow Wireframe Prototyping System - Create beautiful user flows prototypes for your next project
Linked Ideas - A macOS/iOS apps to treat ideas as links of concepts.
React Proto - React application design and prototyping tool
Freeplane - Freeplane is a powerful and free software for building mind maps.
Balsamiq Mockups 3 - New public beta for the popular prototyping tool