Here's an out-of-the-blue idea: use the Google paradigm.
For example, look at gmail. Before gmail, I'd spend lots of time categorizing the tons of emails I'd get, putting them into various folders so that I could find them again (maybe).
With gmail, voila! Just leave them more-or-less all in the inbox, and let the powerful search engine do the on-the-fly sorting for me.
It'd be pretty sweet if we had fewer subforums + very potent search (like bringing in google as the forum's search engine...).