Prestashop - Free Open-Source shopping cart software for Web 2.0

PrestaShop is a free, open-source e-Commerce shopping cart software that allows you to open your own Internet business in just a few clicks. It has more than 310 features include Catalog Management, content management, Product Displays, Site Management, S.E.O, Checkout, Shipping, Payments, Marketing, Client Account, Translations, Security, Localization/Taxes, Analytics and Reporting and lot more.
It supports payment gateways such as Google Checkout, Authorize.net, Skrill, PayPal.