Routing, url to page navigation

[eluser]pieter dekker[/eluser]
I've a routing question.

Say I have a navigation structure on my website like this:

-products
->tshirts
->sweaters
-portfolio
->example1
->example2
-contact
->form
->email

I would like to have the following url structure, for example http://www.mywebsite.com/index.php/products/tshirts or http://www.mywebsite.com/index.php/portfolio/example1

The content is dynamically loaded from the database, new pages can be added, or pages can be deleted (sort of a cms). So I need to dynamically route the url to the right content. How can this be done?