ReadTheDocs - Spend your time on writing high quality documentation, not on the tools to make your documentation work.
Atlassian Bitbucket Server - Atlassian Bitbucket Server is a scalable collaborative Git solution.
Slate API Docs Generator - Create beautiful, intelligent, responsive API documentation.
Visual Studio Team Services - Visual Studio Team Services (VSTS) provides unlimited Git hosting, cloud build for CI, agile planning and continuous delivery.
Natural Docs - Natural Docs is an open-source documentation generator for multiple programming languages.
GitHub Desktop - GitHub Desktop is a seamless way to contribute to projects on GitHub and GitHub Enterprise.