Xmind - Xmind is a brainstorming and mind mapping application.
Freeplane - Freeplane is a powerful and free software for building mind maps.
MindMeister - Create, share and collaboratively work on mind maps with MindMeister, the leading online mind mapping software. Includes apps for iPhone, iPad and Android.
Linked Ideas - A macOS/iOS apps to treat ideas as links of concepts.
Coggle - Coggle is a simple, beautiful, powerful way of structuring information.
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.