PetSmart is running a sale through tomorrow (2/21) on Science Diet dog food! The prices on some of the smaller bags are between $5-$8, so using the $5/1 Any Hill's Science Diet PetSmart coupon in the 1/9 SmartSource insert and the $8/1 Any Science Diet Dry Dog Food coupons will make them free!
When you register and print the $8/1 coupons, you'll also receive two $3/1 Any Science Diet Dry Dog Food coupons as well as a B4G2 free Science Diet Canine cans and a $3/1 3oz. or Larger Bag of Science Diet Canine Treats. The website says you can only print one set of these coupons, but I was able to print two by hitting my back button.
I've heard reports of cashiers and managers giving some people problems with the printable coupons because the coupon's value may be more than the price of the item. Just explain to them that you don't want the overage and that they can simply adjust down the coupon to match the price of the item.