vym - VYM (View Your Mind) is a tool to generate and manipulate maps which show your thoughts.
Axure - The most powerful way to plan, prototype and hand off to developers, all without code. Download a free trial and see why professionals choose Axure RP 9.
Freeplane - Freeplane is a powerful and free software for building mind maps.
Balsamiq - Balsamiq. Rapid, effective and fun wireframing software.
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.
Moqups - The most stunning HTML5 app for creating resolution-independent SVG mockups, wireframes & interactive prototypes for your next project