I found the cheapest price for XBOX cards on Amazon. It sporadically goes down to 40$ per card, which is a great value! Not much to say other than that, it does what it is supposed to do: 12 months of XBOX Live!
I bought my subsription on Amazon because it was a better deal than the standard $60 microsoft or EB charge. Definitely buy it on amazon to save, if your not in a hurry EB usually has a sale around spring and after New Years.