Freeplane - Freeplane is a powerful and free software for building mind maps.

TiddlyWiki - a non-linear personal web notebook

Linked Ideas - A macOS/iOS apps to treat ideas as links of concepts.

wikidPad - wikidPad is an application for storing thoughts, ideas, todo lists, contacts, or anything else that user can think of to write down.

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.

Knowledge Workshop - Learning Management Solutions provides innovative and reliable software for the knowledge worker.