Ok how cool is conductive playdoh?! No seriously. Pretty darn cool!
Samuel Johnson, an undergraduate student at the University of St. Thomas, with the help of his prof. Dr. AnnMarie Thomas, made conductive dough as a fun teaching tool for a middle school science curriculum. Middle school students seems a little old for toying with playdoh but I think K-12 may be a more appropriate demographic.
The end result is a set of squish circuits that teaches kids basic electronic theory.
The Squishy circuit system comprises conductive dough and insulating dough, all made from natural ingredients: water, flour, salt, Cream of Tartar, Vegetable Oil, and Food Coloring (well this isn't natural is it?)
I'm assuming the salt and oil combo is what makes the dough conductive.
Full recipes are both the conductive and insulating dough can be found here.
I think I see a conductive playdoh birthday cake lit of LEDs in my near future.