I wrote a very simple CMS (for a university) that was designed to draw traffic to the less popular pages.
Users could enter keywords and create categories that their content belonged in.
An autocomplete search showed visitors that some keywords were not available.
The more popular the category the more clicks it took to drill down to the content.
Keywords distinguished one page from another while categories grouped them together. The category would not appear until at least two content items belonged to it.
This worked because there were not a very large number of content items. Approximately 20 subcategories in 20 categories was about right in this case