A Complete & Open Source E-Commerce App: Uni-eCart
Uni-eCart is a free and open source e-commerce application that is bundled with all the major features expected.
It is built with PHP and available in several versions where the free one is almost as complete as the others.
Besides a standard e-commerce store, it is capable of running daily-deals and auctions too.
The application supports multiple payment gateways, can display related-items, allows users to discuss + comment and share items on social networks.
On the marketing side, Uni-eCart is again powerful with a mailing list feature and affiliate system.
A detailed admin panel helps managing the whole site easily and stores with any design can be crated with the support for theming.