I have play dough in my classroom throughout the year. It's great for fine motor development, developing concentration, getting the work cycle down, as well as building a sense of order having to keep all their items on their tray as as well as on an art mat.
It's fun to make, easy to gear to whatever type of unit study or holiday is in season, and at craft stores such as Joanne's and Michaels there are tons of different cookie cutters. I often have good luck at Cost Plus World Market for unique cookie cutters.
Here is my favorite play dough recipe
1 cup flour
1/2 cup salt
1 TBS cream of tarter
1 TBS oil
1 cup water
Mix flour, salt, and cream of tarter together.
Mix water, oil, and food coloring together.
Mix in sauce pan over medium heat until it forms a ball.
Take out and knead until cool.
It's fun to add glitter as well :) Just mix it in the water!