When listing via the "sell" form, I'd like to be able to short-cut the initial process of choosing category and then sub-category. Mainly because the long drop-down list for sub-cats is a bore!
I can picture doing this either by putting the sub-cat number into a box at the very start, or by having a list of "recently used" cat/sub-cats available on the first page of the form. A lot of us tend to sell the same sort of things, so I think this could be useful for lots of people.