Interesting paterns created by the agriculture in the nearly desertic mid-west of the United States, possibly Kansas. Circular fields are used so that booms can rotate and sprair water on the crops, in what is called center pivot irrigation.
Update: Indeed this is Kansas. Thanks to jpo for pinpointing the area!
*** Note: It reached Interestingness for 2006-05-15 on 2007-09-29! Thanks everyone!