You can always buy Amazon gift cards through Gyft. You can always get gift cards for a bunch of other retailers. I recommend checking it out 
Amazon is one of the major opponents of Bitcoin. Not only they have refused to accept Bitcoin, but also they have indulged in propaganda campaigns against BTC. If you purchase something from Amazon, you are helping one of the major rivals of Bitcoin. And at the same time Bitcoin is not benefiting out of it, as the gift card was used for the purchase. I prefer online shopping using Overstock.