You can find lots of information about geothermal systems by searching the web. I found an instructable where someone used the temperature of their well water to cool their house. It made me think " If I could tap into this temperature difference in a closed loop system it could be useful " so I started digging.
Step 1: Digging your hole
To get the full benefit from geothermal properties do some research on your area to find the best depth for your zone. Four feet would have been fine for my area, but I wanted to try out a theory I had and by the time I got to eight feet , I had two feet of cool water in the bottom of my hole. Water makes a pretty good heat exchanger and because I live on an island I hit water pretty quick. This lead me to the decision of setting my loop in such an unconventional manner.
Do not try this at home.