This is an idea from Daily Danny http://dannyseo.typepad.com/my_weblog/2008/08/new-crayons-from-old-one.html. I love it! Basically he takes all the old crayons and places them (unwrapped) in n old baking pan in the oven 350 degrees for 10 minutes.
took a bunch of runty old crayons and placed them (unwrapped) in an old baking pan in the oven at 350 degrees for about 10 minutes. He lets them cool and then uses a cookie cutter to cut them in to interesting shapes. A pic is at the top.