Adding Shopping Cart to Web Sites

[Domo]

I can happily design and develop web sites using Dreamweaver and Flash but I've been asked to include a shopping cart.

What's the easiest way to accomplish this? I've not had to do it before now.

Are there tools available which simplify the whole thing

 

[Domo]

What payment gateway will the client be using?

You've lost be there gord. This is my first venture into online transactions - my client has simply stated they expect their customers to be able to order and pay online.