OSCommerce (http://www.oscommerce.com) is a free ecommerce solution, available under the GNU public license.\n\nIf you are looking for other "free" shopping carts, consider PayPal's Shopping Cart. (http://www.paypal.com/cgi-bin/webscr?cmd=p/xcl/rec/sc-intro-outside)\n\nFinally, for a "low-cost" shopping cart that includes the full source code, try AspDotNetStorefront (http://www.aspdotnetstorefront.com). They are ASP.NET-based, and you get the complete source code to modify to your hearts content.
E-commerce?