Classifieds Category - Sub categories..... Not sure how to explain what I need! lol..

Right,

On my site with the classifieds categories, I have top level categories, i.e stuff for sale, property, pets, and then sub levels ie

stuff for sale ->
computers
clothes

pets ->
dogs
cats

At the minute, it shows the taxonomies as one long list... How would I go about modifying the taxonomy output to allow for top level taxonomies and sub level taxonomy selection?

Did that make sense?

Cheers guys,

Danny.