We wrote a custom component we call
RokDocs that uses markdown files hosted on
GitHub to render the documentation pages:
github.com/rockettheme/docs
You can browse the documentation right on GitHub, make changes, merge pull requests etc. This means that we can easily get fixes and edits from our community and quickly merge them into the 'master' copy that gets automatically synced with the live RocketTheme site.
This is not a public component at this time because we do some things that are quite specific to our needs, for example with the image overlays. We have considered making this a product though if the demand was there.
Incidentally we also use this same system for the Gantry documentation:
www.gantry-framework.org/documentation
Hope this helps!