Figma - Team-based interface design, Figma lets you collaborate on designs in real time.
Freeplane - Freeplane is a powerful and free software for building mind maps.
Sketch - Professional digital design for Mac.
Linked Ideas - A macOS/iOS apps to treat ideas as links of concepts.
Invision - Prototyping and collaboration for design teams
vym - VYM (View Your Mind) is a tool to generate and manipulate maps which show your thoughts.