Nice write-up on how to make a playdough like substance for circuits to teach kids the basics of circuits. They have a website too to talk more about the project as a course.
http://www.instructables.com/id/Lead-a-workshop-on-Squishy-Circuits-for-kids-even-/
http://courseweb.stthomas.edu/apthomas/SquishyCircuits/index.htm