HelpNDoc - What is HelpNDoc ? Easy to use yet powerful help authoring environment which can generate various documentation formats from a single source.
ReadTheDocs - Spend your time on writing high quality documentation, not on the tools to make your documentation work.
Dr.Explain - Dr.Explain software is a help file authoring tool.
Docsie - Docsie makes it easy to create and maintain your website documentation, without having to deploy it...
Manula - Manula is an online software for creating user manuals.
ReadMe - A collaborative developer hub for your API or code.