osCommerce
Official Site: http://www.oscommerce.com/
Official Forums: http://forums.oscommerce.com/
Demo: http://www.opensourcecms.com/index.php?option=content&task=view&id=139&Itemid=159

Perhaps the most popular open source e-commerce program availabe. A powerful, feature-rich package with many modules available to extend its capabilities. Has a large community of users and developers that regularly contribute time and support on the official forums.


Zen Cart
Official Site: http://www.zen-cart.com/
Official Forums: http://www.zen-cart.com/forum/
Demo: http://www.opensourcecms.com/index.php?option=content&task=view&id=300&Itemid=159

Another popular e-commerce program. A fork of osCommerce, it sports many advanced features "out of the box", including a templating and override system that allows to you change most of the interface without having to edit or overwrite the original source files. Many modules are available on their website, and a relatively dedicated community of users assists on their official forums.

CRE Loaded
Official Site: http://creloaded.com/
Official Forums: http://forums.creloaded.com
Demo: http://www.creloaded.com/Demos/c33/index.html

A "loaded" version of osCommerce. Basically a standard version of osCommerce with many of the most popular modules already installed/intergrated.

CubeCart
Official Site: http://www.cubecart.com
Official Forums: http://www.cubecart.com/site/forums/
Demo: http://www.cubecart.com/site/demo/


CubeCart is an eCommerce script written with PHP & MySQL. With CubeCart you can setup a powerful online store as long as you have hosting supporting PHP and one MySQL database