I have heard a lot about the different types of ECA stacks, but have not been able to find a product that actually contains asprin, as opposed to willow bark ~ do you know of any products, and what are the differences between willow bark and asprin?

Willow bark is structually the same thing as aspirin. However, because it is not synthetically derived it is not controlled like aspirin. I don't believe that any thermogenic compound has ever contained aspirin. A few years ago when the ECA combination was popular it was "put together" by the user. People would take ephedrine, then take an aspirin and then drink two cups of coffee! In order to dispense a product with aspirin it had to go through a much more stringent process. That is why everybody uses Willow Bark for their "combo" thermogenic supplements. Let me know if you find a thermogenic product that contains aspirin.