Arte Es Vida often features kid-friendly crafts and links amongst the more grown-up ideas, and this is a good (and eco-friendly) one: crayon cupcakes made from broken crayon pieces, melted in mini-muffin tins. She credits the idea to Family Fun where it was originally done as a Valentine's Day craft with heart-shaped molds.
Check her "kid-friendly crafts" tag for more fun stuff, including exhaustive lists of links to craft projects by theme. And don't overlook the big-kid projects, some of which (like this pendant made from shrinky-dink) can be whipped up during naptime.
