Craig,

What is your goal for the price of this board?
Obviously, the more features that you add, the higher the board price will be. So, my list would be this:
- LCD display capability (serial or parallel)
- 1 A/D & 1 D/A with a potentiometer (big one with a
knob)would be nice if there were provision for
multimeter hookup to measure signal from pot. and
signal from D/A
- 16 key keypad capability
- LEDs (min. 8)
- serial port capability