WooCommerce - A freely available eCommerce plugin that enables shop facilities on your WordPress website. Functionality enabling extensions & beautiful themes available.
OpenCart - A free shopping cart system. OpenCart is an open source PHP-based online e-commerce solution.s
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.
Jumpseller - Start Your Online Store! Grow your business.
Hoovers - Search the world's largest database of company and industry information. Find contact information, get competitive reports, build targeted lists
Drupal Commerce - Drupal Commerce