If you're interested in not just the actual code but also the methodology behind it then try http://hotscripts.com. There are some tutorials there that should help you. I've used oscommerce a lot too but I won't touch it now. The code is to intermingled with the html and adding new contributions shouldn't be so darn troublesome. It's in desperate need of an overhaul. Perhaps, a forked version as mentioned by previous poster would be more easy to use particularly if they do a better job in separating the application's layers. If you have to get started fairly quickly and don't have a lot of time/money then osc might be a good idea but just keep in mind what I said. Best Regards!