OmniOutliner - OmniOutliner is a writing app for collecting information, outlining ideas, adding structure to any sort of writing.
Freeplane - Freeplane is a powerful and free software for building mind maps.
Dynalist - Dynalist is a web app that lets you break down and organize your thoughts in the format of lists.
Linked Ideas - A macOS/iOS apps to treat ideas as links of concepts.
Outlinely - Indispensable information organization tool for knowledge workers.
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.