My favorite is http://www.youtube.com/watch?v=M-BhJQqHXfQ from 1958, it shows that even Ansel Adams performed the same things we do now. Photography hasn't changed that much, even with digital cameras!
I bring my 8 year old into the "darkroom" when making contact prints. It shows the "magic" side of photography, as the image comes to life on the paper. It also encourages her to keep trying. It shows her that even with all the failures, success is often only one try away.
I'd love to see more videos that show what draws so many folks to the art, that magic moment when it all comes together!