I'm sure many users already know this but because the information is not very easily found, I thought I'd mention it here.
The Arduino board has 14 Digital I/O Pins and 6 Analog Input Pins.
However, the 6 Analog Input Pins can also be used as Digital Out (and In?) Pins. Naturally, these pins numbered 14 to 19 need to be declared as "pinMode(ledPin, OUTPUT);".
That makes a total of 20.
Hope someone finds this as handy as I have.