I've seen this in some other forums, where they link the subforums directly under the forum category.

Here is a good example of a site that uses it:
http://forums.unfiction.com/forums/

Right now the major subforums are listed under the main categories anyway... all you have to do is add the link. I think it will save a significant amount of "clicking traffic" bandwidth as well as time to navigate.

For example, to get to the section of the board that talks about minlogon, u'd have to navigate as follows:
MP3Car.com Forums > Mp3Car Technical > Software & Software Development > Operating System Optimization > WinNT based

that's 5 hops!

If the subforums were linkified, you could hop straight to Operating System by clicking that link underneath the "software dev" category link, and then click on 'WinNT based' and you're there!

This saves a lot of clicking especially when you are navigating, for example, to the "roadrunner skins" subforum, which is buried in Mp3 tech>Software dev>front ends>RR>skins because you'd only have to click the subforum link 'front ends' from the front main page and then the 'rr skins' subforum link under the RR category heading. you'd save the needless bandwidth of surfing into the RR forum to get to the RR skins subforum, and you'd be in a 5th level nested subforum with only two clicks.