doclori,
Any advice (books, shows) for a little boy that loves physics, machines, and that sort of thing? I've found every physics picture book I could (friction, what is gravity?), but he is ready for something more advanced. He needs something visual like discovery shows. What did your son like?
I'm also not doclori, but rather than just something to watch, what about something he can explore? I'm thinking Erector sets here. There's a bunch of different toys they make where your kid can build something, turn on the motor, and watch what happens.