Freeplane - Freeplane is a powerful and free software for building mind maps.
Minzel - Minzel is a beautiful and free mindmapping tool built for creatives and gives you the power to...
Linked Ideas - A macOS/iOS apps to treat ideas as links of concepts.
TiddlyMap - An interactive concept- and mind-mapping plugin for the personal note-taking software TiddlyWiki based on the Vis.js library. It's free and open-source!
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.
MindNet - MindNet is an effective productivity and learning tool that allows you to take notes, write down ideas, learn, brainstorm your mind, and much more in intuitive graphical mind maps.