RESTful routes and resulting urls

if I have the following in my routes.rb:

map.resources :product_categories

it provides urls such as:

/product_categories /product_categories/1 /product_categories/1;edit etc.

and uses the ProductCategories controller.

how can I keep the same controller (and model) but set up the resources so that I can have any abitrary url point to the existing controller, much like specifying the controller with the old style routes?

-felix