Squirrelcart is a PHP / MySQL e-commerce system with a built-in CMS. It is an open source fully customizable, robust shopping cart. Social sign-in feature lets customers login via Facebook, Twitter, and Google. All products, categories, customers, shipping options, payment options, orders, and every other detail within the cart are stored in a MySQL database. Support for themes. Supports SSL. Fully customizable via templates. Valid XHTML 1.0 transitional markup, with valid CSS stylesheets. Supports Authorize.net, PayPal Pro and Standard, and many other payment gateways (60+). Supports live rate lookups via FedEx, UPS and USPS. Inventory Control feature to keep track of your stock. Support for an unlimited number of products and categories. Order Management allows customer to view their orders and merchant to manage them. Many other features.