The Pickover "ESP Experiment" was pretty amusing, although it would probably be a lot more impenetrable if they just randomized both sets of cards, instead of always giving the exact same sets of cards. The effect would be the same, but it would be a lot harder to spot. After the fifth try, I noticed that the queens were always different in exactly the same way, and from there it wasn't hard to figure out the replacement trick. I'm clearly not as smart as DeLong's rugrat, but then, I suspect that somebody was chortling at the right points in a revealing fashion while the kid was clicking through, thus biasing the sample.