One of my research lab's projects focuses on creating tools to allow children (and adults) to explore engineering in a fun, playful fashion. A few years ago we set out to see if we could develop a way to create sculptable circuits. The result of this inquiry was Squishy Circuits, a set of conductive and non-conductive homemade play doughs that can be used with electronics components such as motors and LEDs. We're happy to say that the project has taken off beyond our wildest dreams and is now used by teachers, parents and kids around the world.
We've been getting lots of great suggestions from users, and have set up a Facebook community where users can share questions, suggestions and pictures. Please join us! Based on email requests that we have been receiving, we will also be launching new educational material on our website (videos, activity guides, and a basic electronics primer for beginners using squishy circuits) this summer.
PS: Recently, I gave a short demo on the project: