Jonathan,
I have a couple of suggestions below, but before I begin to sound all nitpicky, let me say I love your site.
You have indicated you have an issue occasionally with a single subject dominating the visible threads. Here's a little solution that (unfortunately) will probably take a significant programming effort, but would show the full variety of forums.
It involves the forum threads display on your home page. Instead of just allowing the most recent threads to bubble up as new entries are made, program each line to show the latest thread from each of your major categories (excluding the feedback and support, which people can find on their own). So, you would have:
Forum Topic Msgs
Dance Discussion Classes for Men 1
Announcements & Events America's Ballroom Challenge 14
...and so on.
Unfortunatly, I'm a UNIX C++ programmer, not a web guy, or I'd offer some actual assistance, if you were interested.
There's one other little bug I've come across. When you select to go to, say, "Social Issues", if you then select the general topic "Message Boards", you seem stuck in the smaller category. You can select a different category, but the only way to get back to the general latest threads list is to use the browser back button until you get back past where you made the specific selection (or leaving the website completely and returning).