Preschool children need freedom to play with Play-Doh and modeling clay, simply as a muscle-building exercise for the fingers. The more they knead the dough, the stronger their hands and fingers become. Model rolling a ball in the hands, flattening it into a pancake, rolling it into a snake. Demonstrate how to create an exotic imaginary creature, using fingers, tools, cookie cutters, rolling pins and more, and allow their imaginations to take over.
A fun experiment with Play-Doh is to give children two different primary colors, one for each hand. Read a story, such as Mouse Paint. When the mice begin to mix the colors, have the children put their hands together and squish the balls until they make one color.
For take-home projects, provide a bunch of colors to expand upon their creativity. Remember that Play-Doh and many clays will eventually dry if left out. Modeling clay doesn't typically dry out, so it can easily be used and reused.
Different types of Play-Doh and clay are available at local retailers and through school catalogs. Homemade versions can even be made as a class project. Stick to the nontoxic, brightly colored varieties. Try both name brands and off-brands.