Here's one that I make all the time for my dogs. Have also sold them at craft fairs, and they go fast!
2 cups whole wheat flour
1 tsp. baking powder
1 cup peanut butter
1 cup skim milk
Preheat oven to 350
Combine flour & baking powder; in a separate bowl, combine peanut butter & milk; mix wet ingred. w/ dry ingred. and knead together. Roll out to 1/4" thick. Cut w/ cookie cutter (I use bone-shape), bake for 10-15 min.
I make these for all my human family's dogs at Christmas. So simple, and the dogs love them. PS you can underbake them for a couple of minutes and they wont be as crunchy--good for those older small dogs with shakey teeth!