PrestaShop is professional open source eCommerce shopping cart software. Pretty new comer, it is competing against Magento in the full-featured open source ecommerce suite.
Zen Cart is an open source ecommerce shopping software. Built on a foundation of OScommerce GPL code, it provides an easy-to-setup and run online stores. Zen Cart isone of the leading PHP shopping cart.
Magento is a new kid on the block in the open source ecommerce field. It is providing many of the features you are waiting from a modem e-commerce platform: tagging, voting, social networking, SEO compliancy.... A Must See solution.
