Over the years it seems as if Pet Food have been get more expensive. There has definitely been an increase in people looking for Dog Food Coupons, probably due to the the rise in price. I stumbled across what appears to be a pretty good resource with lots of dog food discounts.
The website is Pet Food Chat. It appears as if they have a section on Cat Foods and Dog Foods. The section on Dog Food appears to only have Dog Food Coupons on it right now whereas the Cat Food section is chalked full of Cat Food Reviews and Coupons.
Here are some other great resources on coupons: