This is one of those projects that I wish I'd thought of first. Not only are these stepping stones' construction brilliant, but so are their respective outcomes. Materials to make them are easily found at any big box store and include concrete, cardboard tubing (the big stuff used for poured footings), cooking spray, a piece of chalk, a saw, a tin-foil-covered board, and a rubber doormat with a cool design. Put them all together, and you can probably figure out the directions for making them, but just in case, here's a link to all the details.
DIY Stepping Stones [Nancy Mizelle]