Redmine

While parent/child relations offer a way back from the child to the parent, it's not very flexible. Page categories could help further organize larger wikis. Example: Wikipedia. This is how it could fit in:

To add a wiki page to one or more categories, add the following line somewhere on the page:

category: Hardware, Services, Help

This will actually render a box containing the list of categories linking to the respective category index page. To add the page to categories without rendering this box, wrap it in curly brackets:

{category: Hardware, Services, Help}

Category index pages are automatically rendered and contain an alphabetical list of all pages from a given page category. To link to a category page, add the following to a wiki page:

[[category:Hardware]]
[[category:Hardware|Pages related to hardware]]

Or to index pages of another project:

[[sandbox:category:Hardware]]
[[sandbox:category:Hardware|Pages related to hardware]]