The category collapsing is bugged.
When you try collapse one near the top it collapses EVERYTHING under it instead fo that section.
To make it even less clutters have 3 or even possibly 4 rows of sub categories?
Eg: http://www.bmx-forum.com/forum.php like on this site, there are lots of rows instead of 2 but align it better, like how it is now.
make it look a little cleaner.