As of 2008-10-28, this project may now be found at http://code.google.com/p/open-cart/.
OpenCart is an open source PHP-based online shopping cart system. A robust e-commerce solution for Internet merchants with the ability to create their own online business and participate in e-commerce at a minimal cost.
This is an excellent shopping cart software I ever used. I am hosting my www.daania.com using opencart. It's a very flexible open source. I could do a lot of customization by myself. Though it took some time initially, everyone with some knowledge on php an mysql can make customization without any hassle.
Works, very small, no complaints.
Easy to install and use.
Reliable and stable, thanks php-opencart