So, technically, they aren't "repurposed" since the purpose remains the same...they color. Still, they are a fun way to use up those bits and pieces of leftover crayons, and the kids can help for most of it. And don't start thinking I'm all creative and crafty. This idea came from my mom, who used to make these either with or for her preschool students (of which I was one).
Start with your broken, old crayons.
This is where the kids can help (and we've actually been working on this part on and off for some time). You need to peel the paper off of them and sort them into muffin tins. We used the disposable foil ones. I know you can use shaped molds as well. Check out Etsy for some really cute ones. We sorted ours by similar colors, but you can let the kids go crazy with them.
Then, put them on a larger cookie sheet for stability and put in the oven at 350 degrees. I started worrying that this was too hot and turned them down for a while, but then they weren't melting. They will be very runny, so be careful pulling them out of the oven. I didn't watch to see exactly how long they took, but I'd guess about 15 minutes or so.
Pop them out of the molds after they have cooled. This didn't take nearly as long as I thought it would.
The kids are looking forward to coloring with them this afternoon. The cool thing about these is that they color with a swirled effect. These are really great for toddlers who can't hold the skinny crayons yet, but they're fun for all ages.