Html-Cart - Free html shopping cart program, very easy to install with store manager application. Demo and download available. - http://html-cart.com/
Interchange - Open source alternative to commercial commerce servers and application server/component applications. - http://www.icdevgroup.org/
eComPal - Free service available with varying higher monthly cost options also. Works with QuickBooks. - http://www.ecompal.com/
VIPcart.com - Same day setup on free service. More advanced features on VIP service that's available for fee. - http://vipcart.com/
Mal's Ecommerce - Remotely hosted system that can be built into any existing web site. - http://www.ait2000.com/
eButtonz - Application for building online store. Same day setup. Free version has vendor advertisements. - http://www.ebuttonz.com/index.html
CommerceSQL - MySQL database driven application for larger merchants with many products. - http://commercesql.com/
EZ-Powercart - Free application from company offering hosting services and other freebies. - http://www.ez-powercart.com/
WebPeddle - Application implented on an existing site. Supports linking to ImagineNation credit card processing service. - http://webpeddle.com/
Commerce.cgi - This version includes the ability to use iTransact or AuthorizeNet for credit card processing. Uses the GNU license. - http://www.commerce-cgi.com/