Michael Gasperi latest hack - interfacing the NXT to a servo motor. In practice, this interface can control other analog devices. Here he show how the digital-to-analog converter (connected to the NXT) is used to control a voltage controlled oscillator that produces pulses capable of driving a RC Servo. More details here and in this forums post. Also, Michael used an old IBM 07G0032 keypad in this case, and he has the details here.