Lovely article with some interesting puzzles near the bottom (and top). When I was young, Martin Gardner's puzzle books, along with Raymond Smullyan's 'What Is The Name Of This Book?'[1], introduced me to logic and to the fact that mathematics could be fun - something that was very influential in going on to study maths and computer science. I thoroughly recommend checking them out if you haven't already.

[1] http://www.amazon.com/What-Name-This-Book-Recreational/dp/04...