Fark linked up this bizzare account of the discovery of 400 lb + boulders perched high in the branches of various trees in a remote part of Yellowwood forest, in Indiana.

I lean toward a flood explanation. I used to hike around the Buffalo River valley occasionally in college, and you'd come across all kinds of weird things stuck high in trees... mostly rocks and the occasional canoe. All were caused by the spring floods that rocketed through the valley every year.

Of course, I don't remember anything that big up in a tree. Ah well...