I've been looking for an E-Commerce script which will integrate into an existing design without having to re-create it for zen-cart etc. A few CMS systems allow you to integrate the system into an existing design (solucija.com/home/snews/for example) by including a small section of php and I was wondering if any open source (if possible) scripts could achieve this?
Try avactis: http://www.avactis.com/ It's not free, but it's made to integrate into a site rather than trying to integrate a site into a cart.