I've recently joined Pinterest and found many great ideas to recycle old crayons. My favorite idea is from Martha Stewart ... Heart shaped crayon. This is a very easy project using old crayons, a silicone baking tray and your oven. It only takes 30 minutes and the kids can help. That's my definition of a perfect project!
You can mix all colors together for multicolored crayons. If you want, you can choose your crayon colors to suit a desired color scheme (e.g., use red, pink and white crayons for Valentine's Day themed crayons; red and green for Christmas crayons; or orange and black for Halloween). You can also mold your crayons in a variety of shapes. Your choices are only limited by the available selection of silicone molds at your local gourmet shop or craft store.
You'll need the following:
Old crayons, peeled from their wrappers (select colors to suit your desired color scheme)
A self healing mat or cutting board
A chef's knife
A large bowl
A silicon mini muffin mold (mine makes 24 mini hearts)
A cookie sheet or sheet pan.
Preheat your oven to 150. Place your silicon mold on top of a cookie sheet and set aside. While the oven is heating, chop your old crayons into small bits using your chef's knife and self healing mat. Transfer chopped crayons to a large bowl. (You can separate your crayon bits by color if you want to make crayons in a variety of color combinations.) 
When you have chopped a fair amount, spoon the crayon bits into each well of your muffin mold (keeping the mold on top of the cookie sheet). Be sure to add enough of each color to get your desired color combination. (I went for a multicolored look and made sure every mold had a nice selection of colors.) Fill each well to the top; otherwise your crayons may be too thin.
When you've filled the desired number of wells, put your mold in the oven. (It is important to carry the mold to the oven on top of the cookie sheet, to keep your mold flat. Otherwise, your crayons (and later the melted wax) may spill. Bake the filled mold at 150 degrees for 15-20 minutes, until the crayons melt. When the crayons are melted, remove your mold from the oven. (Again, keep the mold on the cookie sheet!) Set the mold aside to cool. The mold cools pretty quickly. When completely cooled, remove the crayons from the mold by carefully pushing on the underside of each well. If you are having difficulty removing the crayons, try cooling the mold in the freezer first for 20 minutes to an hour.
These crayons are easy to make ... and economical! These are great giveaways for any occasion. The variety of colors you can use means you can give these all year round. Even parents will think they're fun!
