Linux Categories try 4
Use this: http://jqueryui.com/accordion/
With top level categories in the Examples area on the right, and the 2nd level categories as accordion section headings.
I would recommend using the methods discussed here: http://www.mediawiki.org/wiki/Manual:Collapsible_elements to create collapsible navigation boxes. Could also use NavFrame as used by wikipedia (also described on the link above). This would be very easy to do and just requires a few modifications to the CSS created for the masonry items.
In addition, you might consider making each of these navigation boxes into a template so that you can easily insert the same navigation content on multiple pages. For example, Linux_Main would have all navigation links using templates, and the header for each section would link to the intro page for that section of the documentation. Each intro page which would also include the {{System Operation Nav}} template link to show the navigation block for that section of documentation.
