Scrivener - Scrivener is a content-generation tool for composing and structuring documents.
Freeplane - Freeplane is a powerful and free software for building mind maps.
Final Draft - Use your creative energy to focus on the content; let Final Draft take care of the style.
Linked Ideas - A macOS/iOS apps to treat ideas as links of concepts.
yWriter - Free writing software designed by the author of the Hal Spacejock and Hal Junior series. yWriter6 helps you write a book by organising chapters, scenes, characters and locations in an easy-to-use interface.
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.