Maybe lots of folks on here already knew this stuff, but here is an interesting article about the differences between the nutritive values of eggs laid by chickens fed more natural diets and raised free range or pasture style vs chickens fed only commercial feed and raised in cages. Check it out.
http://www.motherearthnews.com/Real-Food/2007-10-01/Tests-Reveal-Healthier-Eggs.aspx
http://www.motherearthnews.com/Real-Food/2007-10-01/Tests-Reveal-Healthier-Eggs.aspx