I have worked with many different e-commerce platforms over the years, From very basic to extremely complex. I have recently come across a relatively new e-commerce platform that has got me hooked.
E-commerce made easy

FoxyCart has created a great set of e-commerce tools that allow you to easily set up a fully functional online store/shopping cart with very minimal effort.
Foxycart offers support for either Paypal payments pro (for credit card payments only at the moment) or some of the more popular payment gateways. as well as support for live shipping rates from Fedex, UPS, etc.
All in all, foxycart packs a nice sales punch. And is my shopping cart solution of choice.

Foxycart: Popup AJAX Cart Goodness


Foxycart Demo Store