Tire swing - Popular Mechanics One Day Project: Kid's Backyard Tire Swing This tire swing project is easy to assemble and hang from a backyard tree branch. Even better, it's a great way to find a new life for a used motorcycle tire.
Wall mounted ball run. This would be great for kids who are too young for the marble runs. Could be used as a music installation if there are movable obstructions in the pipe that make sound when a ball touches them