Free comprehensive PHP shopping cart software Shop-Script FREE.
Our turnkey ecommerce solution is search engine friendly, comes in 100% open source, Smarty template design based, can be installed in 5 minutes, works on most operating systems and provides many facilities including:

Fully functional free shopping cart software,
No programming required,
Easy-to-use web based control panel,
User friendly frontend,
100% open source,
100% template based design (Smarty templates engine),
Multiple language support,
Easy design integration to an existing website,
Products and categories thumbnails,
CSS-compatible design,
Information pages,
Support for dynamic images,
Unlimited number of product categories,
Unlimited number of products,
Unlimited category nesting,
Product stock level control,
HTML descriptions,
Three types of product images,
List price markdowns,
Customers' products ratings,
Special offers marketing tools,
Enable/disable products,
Category HTML description and thumbnail,
Shopping cart,
Shopping cart feature can be turned off, thus giving you an ability to create an online web catalog,
Basic ordering system,
All orders are stored in the database,
E-mail notifications,
Search engine optimized,
Outlined product info (headings, ALTs, etc).

PLUS free customer support and free access to product updates!