For electronics classes or Makers in general, a new (to me anyway) website, 123dCircuits, lets you create a circuit and share it online. It even has an Arduino simulator so you can fully design your shield program and breadboard circuit before risking any sensitive components.
Here is a simple LED flashlight circuit that I designed - well, I designed and built the flashlight before this site existed, but I can show and share it easily with this site. Here is what it looks like in real life. All of the components fit neatly inside of a 35mm film canister with the help of a Dremel and some hot glue.