Adding Sub-Categories

[jetjames]

I'm wondering how I can add sub-categories that will not take up too much space on my forum home page. I'd like to have main categories on the home page, and then show the sub-categories only when the user clicks on that main category. Even doing it like it's done here would be cool, just showing the sub-categories small... Any suggestions?
Thanks!

[Kirk Y]

AdminCP -> Forum Listings Display Options -> Depth of Forums