MkDocs

MkDocs (https://www.mkdocs.org/) is a very minimalistic static page generator that can be used to document your projects. It lacks built-in autodoc features, similar to those in Sphinx, but uses the lot simpler and readable Markdown markup language. It is also really extensible. It is definitely easier to write a MkDocs plugin than a docutils extension that could be used by Sphinx. So, if you have very specific documentation needs that cannot be satisfied by existing tools and their extensions are available at the moment, then MkDocs provides a very good foundation for building something custom-tailored.