UX Flow Wireframe Prototyping System - Create beautiful user flows prototypes for your next project
Freeplane - Freeplane is a powerful and free software for building mind maps.
draw.io - Online diagramming application
SuperNotecard - Introducing SuperNotecard. SuperNotecard is an online writing tool that features virtual notecards to help arrange facts or scenes, track details, organize paragraphs, and clarify your composition process.
UMLGraph - UMLGraph is a professional automated drawing tool that allows the designers the declarative specification and drawing of UML class and sequence diagram.
vym - VYM (View Your Mind) is a tool to generate and manipulate maps which show your thoughts.