Agoracart for ecommerce
One of the top free programs offering shopping cart templates and code is Agoracart. For those small-medium sized booksellers gutsy (or crazy) enough to build their own website it can be a great tool. The free version is fully functional, but some additional features can be accessed by becoming a lifetime member of the Agoracart community for $55USD. The do have a handful of booksellers listed as using the software whose pages would be worth looking at before playing with the program.