The New York Public Library has an archive of over 40,000 historical stereographs, many well over a hundred years old. Stereographs are regular photographs, except in pairs, with the perspective very slightly different. Essentially, stereographs are what you were looking at through your ViewMaster as a kid. And now the NYPL has created a pretty amazing tool they're calling the Stereogranimator that lets users create animated 3-D GIFs from the photos in the archive.
Moving the image back and forth between the two perspectives tricks the eye into seeing depth--it's kind of a lo-fi way to get around that problem of both eyes seeing the same thing. (Regular 3-D beams a different image to each eye.) Here's a recent example:
GIF made with the NYPL Labs Stereogranimator
It's especially cool that the tool, while easy to use, isn't really automatic--you still have to play around with it to get the perspective and speed just right. Go check it out!