This is an old one, but I just (re)found it. I scanned and compiled 12 of Eadweard Muybridge's horse trotting images into an animated gif. This was the centerpiece of my very first website in 1995.
Muybridge made these photos by setting up twelve view cameras and putting trip wires across the horse's path. Then, as the horse passed each camera, it pulled on the wire, which tripped the shutter, and then fell off, so as not to impede the gait of the horse. Muybridge went on to make many animal and human movement animations in this manner and is credited with being the father of moving images.
