GitBook - Modern Publishing, Simply taking your books from ideas to finished, polished books.
Xmind - Xmind is a brainstorming and mind mapping application.
MkDocs - Project documentation with Markdown.
MindMeister - Create, share and collaboratively work on mind maps with MindMeister, the leading online mind mapping software. Includes apps for iPhone, iPad and Android.
Docusaurus - Easy to maintain open source documentation websites
Coggle - Coggle is a simple, beautiful, powerful way of structuring information.