Are there any other options besides Ecwid for online stores through Nation Builder? I'd like to be able to review other options as well.
Kelly, Americart and Ultracart are good options as well. You can see the basics from them here - http://www.americart.com/f_setup.php - and here - http://www.ultracart.com/online-shopping-cart/faq/
Our customer Bullfrog Films uses Americart - you can see that implementation here: http://www.bullfrogcommunities.com/