Wow I hadn't noticed that come along last summer. Here is the national geographic article:
http://news.nationalgeographic.com/news/2009/06/090615-stonehenge-tombs-crop-circles.html
Also, for fun, here is the google map photo of the same field. Notice how you can't see any of the marks!
http://maps.google.co.uk/maps?oe=utf-8&client=firefox-a&q=Damerham&ie=UTF8&hq=&hnear=Damerham,+Fordingbridge,+Hampshire,+United+Kingdom&gl=uk&ei=FSm7S_e_BZy60gSbt534Bg&ved=0CAsQ8gEwAA&ll=50.937439,-1.875272&spn=0.005443,0.006888&t=h&z=17