sensor - How do I get an Arduino (5 V) and MPR121 (3.3 V) to talk?

I have the Sparkfun MPR121 I2C Capacitive touch sensor breakout board

I have read that it uses 3.3 V, I know that I can't just connect up the 3.3 V power supply output from the Arduino as the communications lines would require 3.3 V as well. How do I connect up the other lines?

I have found a tutorial at Sparkfun's website. The 3rd diagram using the diode - would that be the best way to interface the sensor to the Arduino?

Any ideas or information would be great, my knowledge is pretty low.