Note, however that the resistance values shown by mspguy may be a bit high given the input impedance of the Arduino. I would consider scaling them to 1/2 or 1/3 the values shown.
its not so bad, but a fair point. the source resistance is 24k and the datasheet says the ADC is designed for a 10k output impedance. Running the ADC at half the speed would work too. I'm always stingy with power ;) Thats why I'm an MSP430 fan.
If it were me, I'd use whatever two resistors I have around that are close to a 1:4 ratio and give a 10k-100k output impedance, then calibrate it. but I had to choose some numbers for the sake of the forum.