Over the years, I have tried several payment systems and shopping cart solutions. Of all, I still use ClickBank and Paypal. For shopping cart, I used 1ShoppingCart for sometime but now moved to PremiumWebCart because 1SC doesn't handle Paypal recurring (surprise!!) wheres PWC does. I also use Authorize.net for payment gateware and Powerpay as the merchant account provider. Hope this helps other marketers.