I used the WiiChuck.h library and the WiiChuck example from the same page to get the data from the Wii nun chuck.

white – ground
red – 3.3+v
green – data
yellow – clock

Instead of cutting the wires of the nun-chuck, I used a Wiichuck Adapter from FunGizmos. It makes it easy to connect the nun-chuck to the breadboard. The data collected can be seen in the serial monitor for the Arduino software or can be displayed using a Processing software example of a RGB cube. All of this can be found on the WiiChuckClass section in Arduino Playground.

WiiChuck.h, WiiChuck.pde, WiiChuck-RGBCube