MicroView Digital Compass
Contributors:
AGlass0fMilk
AGlass0fMilk 
Resources and Going Further
There are a many more cool projects you can make with the MAG3110 sensor. If you combine the MAG3110 with a few other sensors, you can make a variety of projects that involve location and orientation sensing.
Check out Shawn Hymel's Adventues in Science: Using a Magnetometer as a Compass and example code for ideas:
For more sensor fun, check out these other great SparkFun tutorials:
MS5803-14BA Pressure Sensor Hookup Guide
Breakout of MS5803-14BA Pressure Sensor to measure the absolute pressure of the fluid around them to determine altitude, water depth, or any other tasks that require an accurate pressure reading. This includes air, water, and anything else that acts like a viscous fluid.
Are You Okay? Widget
Use an Electric Imp and accelerometer to create an "Are You OK" widget. A cozy piece of technology your friend or loved one can nudge to let you know they're OK from half-a-world away.
Flex Sensor Hookup Guide
An overview of the flex sensor - a bendable variable resistor. Plus, example circuits and Arduino code to get you started!
Magnetic Levitation
This tutorial will show you how to build a magnetic levitation circuit using common parts.