There is a very nice exhibit like this at The National Museum of Emerging Science and Innovation in Tokyo. White and black billiard balls are used. The first 8 balls are the address (to different stations around the room), the next 8 balls are the character you want to send. A kid arranges the balls in one of the sending stations and then releases them into the internet. The balls flow through several 'routers' (contraptions that look like they are based on old telephone technology). The balls flow to the destination (to which the kid has run over to and is waiting for his balls to arrive) and then the character is displayed. My 6 year old played this for a long time and would have played it all day.

There is a picture here at the bottom of the page. There is also contact information. I'm sure you could get a detailed description of its construction if you wrote them an email.

Good luck!

I thought she was happy right where she was. At least, I was always happy. Quick, Dr. Tiki, you'd better write a prescription!

in democracies, great men will eventually come to power at the times of need.

'Eventually' is starting to wear a little thin around here...