Doxygen - Generate documentation from source code
Natural Docs - Natural Docs is an open-source documentation generator for multiple programming languages.
DocFX - A documentation generation tool for API reference and Markdown files!
Daux.io - Daux.io is a documentation generator that uses a simple folder structure and Markdown files to...
Sandcastle - Sandcastle produces accurate, MSDN style, comprehensive documentation by reflecting over the source...
swagger.io - Swagger is an open source RESTapi Documentation Tool.