I found the tip "Alternative Default Routes" from "Rails Code Snippets" very helpful. I wanted to customize the look of URLs in a Rails application and this helped me although it wasn't exactly what I wanted.
I prefer :controller/:id/:action formatted URIs to :controller/:action/:id. For instance, "people/56/edit" to "people/edit/56". This is a simple matter of taste and has no real benefits other than being a bit more intuitive to certain brains.
It's also a bit harder to do than you might expect. You need to replace the default :controller/:action/:id route with the following:
map.connect ':controller/:action',
:requirements => { :action => /\D+/ }
map.connect ':controller/:id/:action',
:action => 'show',
:requirements => { :id => /\d+/ }