I think there is a Google Chrome Extention/Widget that embeds a Bitcoin checkout. At point of sale you used bitcoin to purchase a giftcard, which immediately credited your account (well, 3 confirms) with the giftcard amount and you could checkout. I can't remember the name, "Honey" is coming to mind, so maybe try searching for that?
Bingo:
http://www.joinhoney.comThe Amazon->BTC feature is under development.