Canon Photo Paper Plus: Buy 1, Get 4 Free of the same item
The Canon USA store has a rather unusual promotion, you buy 1 unit of photo paper and you get 4 of the same item for free. These are the eligible Canon photo papers. You add 1 unit to the shopping cart, and the shopping cart automatically adds four more of the same to your shopping cart and marks them as free. No coupon code is needed.
NOTE: If after you add the item to the shopping cart you don't see four free items, it likely means that they are running out of stock. One of the items is already marked out of stock, however, some of the others may be running out as well. If you don't see four free items automatically after you add to cart, it likely means they are out of stock.
The terms of this promotion are, per the aforelinked page:
"Offer valid November 11, 2012 12:01 a.m. through December 8, 2012 11:59 p.m. ET. Offer valid in U.S.A. only, and void where prohibited, taxed or restricted. Availability of certain items may be limited. Limit of ten of any one item per order, subject to availability. Order will be shipped to a street address in the 50 United States or the District of Columbia only. Dealers, distributors and other resellers are not eligible for this offer. Offer subject to Canon Online Store Terms of Sale."