What are some alternatives?
PayKickstart - PayKickstart is the ultimate shopping cart and affiliate management platform, empowering online Entrepreneurs and digital publishers with the tools to sell their products online.
WooCommerce - A freely available eCommerce plugin that enables shop facilities on your WordPress website. Functionality enabling extensions & beautiful themes available.
Selz - Seriously Simple Selling
OpenCart - A free shopping cart system. OpenCart is an open source PHP-based online e-commerce solution.
Shopio - Shopio is an all-in-one hosted shopping cart solution.
Shopify - Shopify is a powerful ecommerce platform that includes everything you need to create an online store and sell online. Try it free for 14 days.