If you want to add a simple shopping cart to your site, this is a good start.   It keeps track of returning users without using cookies.   They check off items on your pages then click "add to cart. "  It will add shipping etc. to the final total, then when they click "purchase", you are notified.   Their email is sent to you so you can contact them about payment. To deploy, simply add a checkbox code to each item on your site. As the user checks off items, they're automatically remembered for checkout. Considering how simple this script is to set up and install, it is quite amazing how many features are available. There is also a database script available which can integrate with this shopping cart.