I have done this for SEO reasons on my application soccertackle.com for products and categories
in the routes.rb file i have created
# named routes for categories map.connect ':controller/:action/:id/:category', :controller => "shop", :action => "list"
# named routes for products map.connect ':controller/:action/:id/:item', :controller => "shop", :action => "view"
and have used an application_helper.rb method using gsub to change the format of the :item or :category parameter in the url and called this method in my views.
I'm sure that this is not the best way to do it but it does mean search bots see a different page for every product and category in the shop and the title of the product or the category is the name of that page instead of realising that it is one dynamically generated page .
Of corse you can still access the pages without the :category or :item parameter on the end of the url
I hope this helps and will be checking back to see if any one has any better ideas.
