Here's an idea: order products online, and then pay using regular 'ol dollar bills. Intrigued? That's exactly what Walmart has begun offering on its website today with its new Pay With Cash service. It's no different from initiating a normal web order, save for being another -- and potentially convoluted -- option to hand over your funds and checkout. After selecting PWC, you'll receive an order confirmation, which then allots you 48 hours to print it out and present it your local Wally World. From there, you can choose to pick up the item in store or have it shipped to your house -- in effect, stripping away some of the key conveniences of