Not only is homemade play dough much cheaper than the store bought stuff, you also know exactly what has gone into it, so it's safe for your little ones (especially if they can't resist tasting it!). It is also, in my opinion, better! and nicer to play with!
1 cup plain flour
1/2 cup salt
1 tbsp vegetable oil
2 tbsp cream of tartar
1 cup water
Assorted food colouring
When you're done - the kids can play til their hearts content! My little boy loved pressing his toys (legos' pens, cars etc) into it to leave impressions. After all the playing is done, you can store it in some little airtight containers or jars (I used old baby food jars), or wrap it in plastic wrap, and it will hopefully last a fair few more playtimes! You can even freeze it if you want to save it for a rainy day.
Enjoy!