I gave a talk to my daughter's middle school class today, on the history of computers. I got lucky, I started out by asking them what questions one might ask about the history of computers and what I got from them had about a 60% overlap with what I had planned to cover. Then they didn't want to stop asking questions, some somewhat random. The school's computer projector turned out at the last minute to be missing--I should have commented on the dangers of dependence on technology. But I always somewhat enjoy having to wing it when the technology is down; the pieces tend to come together in interesting ways.