As already mentioned free coloring pages are a great way to teach your child all sorts of things, numbers for example. There are different ways this can be done, one way would be to simply have the number somewhere on the page, such as the number 10, and then somewhere else on the page would be an object or animal cleverly twisted into that number. There could also simply be 10 of something on the page, you can get your child to color the page in and then count out how many apples for example there are, which will obviously correspond to the number on the page.
You can even print out some and hold a coloring competition amongst your kids or your class. It is all too common for the coloring sheets that are given out and taken home to become lost, torn, or crumpled up. Obviously such damaged coloring pages are no use for the competition anymore. Parents can be instructed to go online and print out replacement printable coloring pages. It only requires a computer, Internet connection, and a printer to come up with such a contest entry replacement.