I bought the little motor and switches to make the timer in the Nuts&Volts issue a few months ago but haven't gotten around to wiring it up. little 120v timer motor and you cut a cam out of 1/4" plywood to hit the SPST switches to give you a real red, yellow, green cycle...was like $5 for the parts...no fancy electronics or anything so it's more of a mechanical build if that's more your thing. you can get a copy of the article on their website I think...
The motor is a little appliance motor from some old electronic supply place that must buy out old stock, because the date on the motors (I bought 3 since I have 3 different lights) were all stamped 1964! thought that was pretty cool...