OpenCart - A free shopping cart system. OpenCart is an open source PHP-based online e-commerce solution.s
Allomani - Allomani is an E-Store with the shopping cart for online shopping websites, hosting & designing, Paid services, etc.
AbanteCart - Free, open source, shopping cart/ e-commerce platform.
Zen Cart - Zen Cart
Selz - Seriously Simple Selling
PrestaShop - Create your online store with PrestaShop's free shopping cart software. Build an ecommerce website for free and start selling online with hundreds of powerful features.