While on vacation I impulsively bought fertile chicken eggs from a farm stall. Needing to incubate them immediately, I cobbled together a rudimentary incubator from a styrofoam cooler and a few bits and pieces. A PID controller was the perfect device to govern the temperature.
Converting an ATX power supply is a great way to get juice to your electronics projects. With the ATX breakout board from Dangerous Prototypes you can do it while waiting for your toast to pop up, and it looks pretty good too.