I have two elementary-aged children who bring home pencil boxes full of broken crayons (and markers and pencils and all kinds of other stuff) at the end of each school year. Yesterday my daughter and I sifted through those boxes, pulled out the "keepers" and bagged up the pieces. I've seen pictures of things that people have done with old broken crayons and thought I'd give one a try.
One of my students got me this pi ice cube tray this year:
Then I popped the tray (on an aluminum-covered cookie sheet) in the oven at 250 degrees for 15-20 minutes.