You Need A Wiki - Create a wiki with Google Docs
HelpNDoc - What is HelpNDoc ? Easy to use yet powerful help authoring environment which can generate various documentation formats from a single source.
Docsify.js - A magical documentation site generator.
HelpSmith - HelpSmith is a help authoring tool to create CHM HTML help files, manuals, and PDF documents.
markdown to web - Convert markdown to online web page
Adobe RoboHelp - Adobe RoboHelp empowers organizations to deliver engaging help and policy content across mobile devices, formats, and platforms.