I've seen a couple of programs on crop circles. One of them had a video of a flowing light that was over a field where a crop circle appeared, but I think it was later proven to be fake.
They are obviously artificial, so, living up to my chosen nickname, I tend to attribute them to the only known intelligence on earth that can make them--humans. I can be convinced otherwise, however.
Personally, I would love to see one up close, a "fresh" one, to really get a feel for what they are like. It's frustrating to only have "after-the-fact" information. Can you imagine being a farmer and finding one of these things in your field?
This video seeks to show the geometric component that goes into the creation of these Crop Circles. It comes with music for the ocassion so turn up your speakers.