...another resource from the "documentation gold" category...
The Infinispan project just finished migrating their website to Awestruct and their documentation to AsciiDoc (specifically Asciidoctor). This is yet another great reference point, especially for large projects.
To bring the community up to speed with the new workflow, project lead Manik Surtani gave a video hangout to explain how everything is setup.
It's without a doubt the best explanation I've heard about how these technologies fit together and the motivation for adopting them.
The Infinispan documentation includes a section about how to contribute to documentation that goes into more detail about how to use the tools. Furthermore, it gives advice on how to use language effectively in documentation, something I've never seen in any other contributor guide.