Stretchofoam

Ingredients:
Acetone (at least enough to fill a coffee cup half way)
styrofoam (the more you have, the more it will make)
1 coffee cup

Fill the coffee mug with about a quarter inch of acetone. 
Place the styrofoam in the acetone. It should fizzle. Keep
adding more styrofoam until you reach a good sized blob. You
can pick it up and play with it. Stretchofoam can be washed
if you do not wish to get acetone on your hands because it 
may dry your hands out, but by washing it loses some of it's
stretchy properties.