I figured out this deal last year. Best Buy always drops $100 iTunes cards to $80 over Black Friday weekend. Free shipping included. You are limited to 3 per order. But not 3 total. I just ordered 15 cards (yes, I spend that much on software and digital publications easily in a year). The codes work on iTunes, the iBook store, and the Mac App Store.
Enjoy.
Direct Link – http://www.bestbuy.com/site/Apple+-+%24100+iTunes+Gift+Card/4056157.p?id=1218452832749&skuId=4056157