GitBook - Modern Publishing, Simply taking your books from ideas to finished, polished books.
Evernote - Bring your life's work together in one digital workspace. Evernote is the place to collect inspirational ideas, write meaningful words, and move your important projects forward.
MkDocs - Project documentation with Markdown.
Workflowy - A better way to organize your mind.
Docusaurus - Easy to maintain open source documentation websites
Ghostnote - Add notes to anything.