Fantastic slideshow here from Slate (or click the picture).
"Now, with the advent of satellite technology, we've become largely accustomed to the wonder of seeing the Earth from so distant a perch. But until fairly recently, encompassing images of the planet were a novelty that gave its residents an entirely new perspective on the planet. Here, in honor of Earth Day, is a slide-show history of aerial photography, as shot from a variety of vehicles. And pigeons."