I love being crafty with Caleb. One fun craft we have done is make rainbow crayons. To make them, simply take broken crayons, make sure they are in small pieces (A whole crayon should be split into 4 or more pieces) and put them in a cupcake tin. I have done stars and hearts (I bought the heart one on clearance after Valentine's Day!!) but the hearts were much easier because it was silicone.
I let Caleb decide which pieces he wants in each cup. We fill each one about 2/3 of the way up with crayon pieces and make sure that each one has a mixture of light and dark crayons. I've also seen where you make each one a solid color, but I like the rainbow effect more.
Put the tin in the oven on a low setting (I did 275 degrees) and let the crayons melt. This usually only takes about 5-7 minutes.