This is just a quick arduino tip. Even though there are only 14 digital i/o pins, the arduino has more. Analog pins can also be used as digital. Analog pins 0-5 are used as digital pins 14-19. In case you don't need all your analog pins and need more digital outs, i suggest this solution.
more info on: http://www.arduino.cc/en/Reference/DigitalWrite
Also, analog pins can be used to read multiple buttons, as in this example: http://www.instructables.com/id/How-to-access-5-buttons-through-1-Arduino-input/
this tip is credited to instructables user riaancornelius