clocks contest, and I settled on a sundial. I then opted for an analemmatic sundial, where the gnomon is vertical and its location changes. I haven't made the sundial yet, but I have written a perl script that generates plans for one, with all the dimensions.
This will make a nice educational project to do with kids. Here are complete instructions.
You can then draw it in chalk on a driveway (and then maybe paint it permanently), and then stand on the correct date (along the vertical center line) with your body being the gnomon. Or you can just print out the design on a piece of paper, point it correctly, and hold a pencil upright on the correct date (along the vertical center line) to get the time. You can even use it as a solar compass if you know what time it is. You hold the pencil upright on the correct date, rotate the sundial until it shows the correct time, and use the "N" arrow.