Depends what you are after,
If you want a PHP page for display on your site, the firetank advanced sitemap will do what you need, just set it to display all products
http://www.firetanksoftware.com/fts/customer/X-cart-Site-Map-advanced-sitemap-pid-70.html
If you want to actually output to a CSV file lists of products and URL, take a look at our shopping feed generators, one like the googlebase/froogle one will do it and you can alter it to match your requirements
http://www.firetanksoftware.com/fts/customer/X-cart-Shopping-Feeds-cid-26.html