Hip2Save has a great post about Cesar's giving away dog food start 8/22. Go here for the full details of the promotion and another link to a buy one/get one coupon.
Walgreen's also has a .50 store coupon for Purina Dog Food 3.5-4lb bags. Although I am less than please with Walgreen's right now about their inconsistent Register Reward policies and when they will print versus will not. I have contact corporate about it. Once I get an answer I'll make sure to post it.