Okay A hack I wrote for our 6.05 board - never released it because the coding wasn't exactly brilliant.
What it does:
In the User's profile, they have the option of which forums they want to hide. And an option for whether those should be hidden from Daily Topics aswell. And it has a default hide for guests aswell (via a wordlet)
If you goto our boards and begin to register you'll see the options I mean. (although they were split into two boxes, but since adding and deleting forums it seems to have confused it)
What I did was to make HTML comments in the rows part that wrote each line for the forums.
i.e
