Internet Routing
Make a presentation on how Internet routing works and follow with a group activity of Internet routing. The activity is to have each student in a group with 4 or 5 people acting as a router or end point and pass a piece of paper which has all the routing information, such as source address (the sender student name) and destination (the receiver student name.) Based on the grade level, the complexity can vary. I've been doing this with grades 4 and 5 and both went very well. The kids have learned not only from where they get email and web pages, but how.
Thanks to John Du in Oregon for providing this activity idea.