http://daux.io/ is a Doxygen-like documentation generation software that is geared towards simpler doc structure and the use of Markdown for the syntax. It's free and on GitHub.

While the wiki is nicely editable and its syntax is simple enough if needed, should we consider having Sphere's documentation downloadable and in a format such as that daux.io generates? Obviously we'd need to update the docs first if that's the case.

Sounds like a good idea to have a downloadable version of the wiki. If you ask me, it should be a timed snapshot of the wiki, available as a download.