I got this fabulous recipe from Lisa Murphy's Ooey Gooey Tooey book. You will need:
1 box of cake mix (any type will do)
2 cups of flour
1 1/2 cups of salt
6 tsp of cream of tartar
6 tbls oil
3 cups of water
Mix it all in a bowl (we used an electric mixer). Then pour into a pot and cook on medium heat until the dough begins to form a ball. Plop it on the counter and let it cool. Knead until it is soft and pliable. This play dough, if kept in an airtight container) will last for weeks. It is so fun and smells incredible.