Hi Alberto,
ClarionShop is written in NetTalk (actually it's still NetTalk 5) so it's a "working example" of a shopping cart app - but that said - you're asking the question in the wrong way.
Think about a "shopping" app if it was a normal clarion program you'd code it as a bunch of browses and forms. So it is with a web app. Obviously the exact combination of browses and forms depends on you - and will vary from site to site. But all the components of a "shopping cart" are trivial when you have data tables, and browses and forms at your disposal.
cheers
Bruce