Can I specify that analog pins be used for digital output? http://arduino.cc/en/Reference/pinMode notes that


  The analog input pins can be used as digital pins, referred to as A0, A1, etc.


Is it possible to configure these pins as digital output pins as well?
Yes.

http://arduino.cc/en/Tutorial/AnalogInputPins states


  The analog pins can be used identically to the digital pins, using the aliases A0 (for analog input 0), A1, etc. For example, the code would look like this to set analog pin 0 to an output, and to set it HIGH:


pinMode(A0, OUTPUT);
digitalWrite(A0, HIGH)


There are several caveats on that page regarding this.