I have 28 web sites and none of them have a shopping cart or sales mechanism. Now I have a new web site in which I need to take on-line orders for one product.

Can anyone give me some advice as to the best or easiest to use shopping carts, merchant accounts and payment processing mechanisms?

I have used many types of these but am unfamiliar with how to set up or which ones to choose. Thanks for any tips, suggestions, etc.