Here's a suggestion - get the URL right when you link to your site. I'd start with as few divisions as possible (also, it's tough to get to a full forum list, so I have no real idea what your existing categories are - maybe you should make the front page a list of forums rather than recent posts.
I would suggest you to make a search on Google, find what competitors are doing and make it all a little simpler. Than once the forum gets bigger you add more categories (eventually members will ask for more if you put a "Suggestions & Comments" section).