My Dad did the coolest one for my fifth grade class that everyone still remembers. He showed us how binary addition in a calculator/computer works by giving us all 0 or 1 notecards. Then since the class is already arranged in a grid, each row is a single digit (8 bits). Then He gave input numbers and we raised our cards according to which bit we were an the person to the left of us.
Honnestly I don't remember the specifics but it was so awesome to see something as abstract as a computer/processor shown to us in a way we could understand and participate in. And the layout of the classroom just happens to be perfect for it.
That's an interesting idea. You could take three groups of kids, group 1 is register A, group 2 is register B, group 3 is the output, and you have one for carry/overflow. You can add or remove bits and make other flags to get everyone included. Then you just tell them the rules for any operation you want to run!
For example, adding A and B together you do from right to left, and carry gets to raise his hand when you overflow.
You could do other simple operations like subtract, shifts, ANDs and ORs, etc.
Honnestly I don't remember the specifics but it was so awesome to see something as abstract as a computer/processor shown to us in a way we could understand and participate in. And the layout of the classroom just happens to be perfect for it.