Plot Factory - Online story planner, organizer, and writing application.
Mindmapper - Be more creative and get more done. Process your thoughts with a mind map and implement with a planner.
World Anvil - World Anvil is a worldbuilding tool for Authors, Storytellers and worldbuilding lovers.
Coggle - Coggle is a simple, beautiful, powerful way of structuring information.
Scrivener - Scrivener is a content-generation tool for composing and structuring documents.
mind42 - Mind42 is a free online mind mapping software.