I've been wanting to try this little project for quite a while now! I can't even remember where I first saw it, although since then I've seen it several places.
I used to throw away the broken bits of crayons from the kiddos' crayola box, but recently I've started saving them all whenever I clean out their box. This is a great way to recycle those broken pieces!
Next, preheat your oven to 175F. Then take your old muffin tin (or line one that you plan to still cook in with foil papers). I found this heart silicone pan on clearance at Michael's and it worked GREAT! You can also use candy or soap molds. Fill each slot with an inch-thick layer of crayons. Bake for 30-35 minutes or until crayons are melted.
Allow the crayons to cool completely, then pop out and grab some coloring books!