I recently published an instructable for creating a working 'Steampunk Compass' .

Starting off with this build its very easy to extend it and create a device that instead of pointing north will point to any programmed coordinate. Something that can always point you towards home, or to a geocache.

Step 1: The Parts.

In addition to the parts layed out in the 'Steampunk Compass' instructable you will only need the following;

EM-406A GPS Module

Step 2: The Build.

Follow the build for the 'Steampunk Compass' . The ony additional step is to connect up the GPS module.

Either wire it up directly; http://wiring.org.co/learning/libraries/basicpositioning.html
Or spash out and get a shield; http://www.sparkfun.com/products/10102

Step 3: The Source.

As with everything in this instruction the souce is an extention of that in the 'Steampunk Compass' instructable.

Using the TinyGPS library your current position is taken and the direction to the final location is calculated. Taking the compass direction of the box away from this direction gives you the required heading, and this is whats displayed via the servo.

Your final destination is specified in the attached code;

#define DESTINATION_LATITUDE ( 37.916553f * DEG_TO_RAD ) // destination imitos
#define DESTINATION_LONGITUDE ( 23.815278f * DEG_TO_RAD ) // destination imitis