WordPress.org

Ecwid is a free full-featured shopping cart and an e-commerce solution that can easily be added to any blog or Facebook profile. It offers the performance and flexibility you need, with none of the hassles you don't.
"Ecwid" stands for "ecommerce widgets".

There are eight key advantages to Ecwid:

• It's free.
• It has AJAX everywhere and supports drag-and-drop.
• It can be easily integrated to any existing site or Facebook profile in minutes.
• It can be mirrored on many sites at the same time. Add your store to many sites, manage it from one place.
• Integration with social networks. Run your own store on Facebook, mySpace and many others.
• Simple to use and maintain. For both store owner and customer.
• Lightning fast. New-gen technologies make Ecwid much faster than usual shopping carts regardless the hosting service you use.
• Seamless upgrades. You just wake up one day and enjoy new features.

Links

• You can see the demo there: http://www.ecwid.com/demo-frontend.html
• More features: http://www.ecwid.com/key-features.html