XMind

It is open source software for brainstorming and mind-mapping.

XMind helps the user to capture their ideas, organize them into different diagrams, and share those diagrams with other users. XMind supports mind maps, Ishikawa diagrams (also known as fishbone diagrams or cause-effect diagrams), tree diagrams, logic diagrams, tables. XMind is often used for knowledge management, meetings, task management, and time management.

Mind maps/fishbone diagrams are created by simply pressing Tab and Enter to create new items and sub-items. You can add and modify item boundaries, relationships between items, markers, labels, text labels, links, audio files, and graphics to the chart. Various files can also be attached.