I like playdough and I've rarely met a child who doesn't. The stuff in the little canisters will work, but homemade is infinitely better.... and lasts for quite some time in a big ziploc bag.
1 c. flour
1/2 c. salt
1 c. water
1 tbsp. oil
2 tsp. cream of tartar
Food coloring (a few drops at a time)
1. Combine all ingredients in a pan and stir. Cook over low heat, stirring until a ball forms.
2. Add food coloring and mix thoroughly until desired color.
3. Cool on foil. Store in covered container.