So this is an age old problem with forums…
Each added category does provide some extra value but also adds increased complexity at every level. Increased cognitive load when being required to choose a category when posting a new topic… Increased navigation complexity when moving through the site… And Increased time spent by mods to manage and edit mis-categorized posts.
Google+ was designed with minimal categories and good search. Their approach was to provide with search function what other forums provide with category complexity. This forum does have a very good search feature and you can bookmark searches to create lists of things you’re interested in.
Here’s another idea: This forum does have tags. They are disabled right now, but tags can be added by members at time of posting. You can search thru tags to find a good one or add a new one right in the post box.
Perhaps using one large category of resources plus many different tags provides a good middle ground of simplicity and complexity.