We have On-the-Go bags with activities for the kids to do in the car. They have a bag of old crayons with paper and coloring books, and other stuff to keep them from killing each other in the back of the van. For the record, I don't leave the bags in the car. They're in a room just before the front door in our house, and I grab them on the way out, and bring them back on the way in. It makes use of 2 sets of old crayons in my house :D

You can make crayon patties with them. You chop up the crayons and put them in a mini muffin tin and cook them at 200 for a bit and then you have new crayons. My kids love to mix and match the colors. DS likes to make camo ones (green and brown) and dd is currently into pink/purple combos.

These would make a nice gift for a todler along with a pad of paper or a coloring book.

You could donate them to the school art teacher, your church for use in Sunday School classes, to a local children's museum.