HowHive - Knowledgebases for teams and companies of all sizes. Knowledge sharing and finding made simple.
GitBook - Modern Publishing, Simply taking your books from ideas to finished, polished books.
Raneto - Open source, flat-file Knowledgebase platform that uses static Markdown files
MkDocs - Project documentation with Markdown.
openKB - openKB is a Markdown Knowledge base application (FAQ) built with Nodejs and ExpressJS.
Docusaurus - Easy to maintain open source documentation websites