eCommerce

PHP

Magento

Seotoaster

http://prestashop.com
http://www.ubercart.org
http://www.zen-cart.com
http://www.oscommerce.com

Extensions CMS

WordPress
http://getshopped.org e-Commerce

Joomla
http://extensions.joomla.org/extensions/e-commerce VirtueMart
http://extensions.joomla.org/extensions/extension-specific/virtuemart-extensions
http://virtuemart.net

Drupal
http://drupal.org/project/ubercart Ubercart
http://www.drupalcommerce.org Drupal Commerce

MODx
http://modx.com/extras/package/visioncart VisionCart
http://modx.com/extras/category/e-commerce

SilverStripe
http://code.google.com/p/silverstripe-ecommerce eCommerce
http://www.silverstripe.org/silvercart-module SilverCart

Discussion

http://php.opensourcecms.com/scripts/show.php?catid=3&sortby=rate asc eCommerce
http://www.hongkiat.com/blog/setting-up-your-first-online-shophttp://www.sitepoint.com/the-world-of-ecommerce-solutions-simplified-for-your-business/#post-52343