If you are looking for an easy way to turn your nation into an online store, give Ecwid a try and you could be up and running in just minutes.
Ecwid is a shopping cart software startup providing a cross-platform, AJAX-powered store builder widget that enables users to easily embed a store into any website and social network page. The service is free to shops with fewer than 100 products, and monthly plans for bigger stores start at $17. You can take payments through major vendors including PayPal, Google Checkout and Authorize.net.
Embedding their widget into NationBuilder is a 5-minute endeavour.