JSDoc - An API documentation generator for JavaScript.
Dr.Explain - Dr.Explain software is a help file authoring tool.
GitBook - Modern Publishing, Simply taking your books from ideas to finished, polished books.
HelpSmith - HelpSmith is a help authoring tool to create CHM HTML help files, manuals, and PDF documents.
Developerhub.io - All-in-One Platform for Online Documentation
MadCap Flare - Documentation for Any Audience, Language or Format