This has nothing to do with poker directly, but this week's Sunday Puzzle on NPR is an interesting exercise of your probability-thinking muscles.
Next week's challenge: The following challenge is based on a puzzle from a Martin Gardner book, that may not be well-known. Out of a regular grade school classroom, two students are chosen at random. Both happen to have blue eyes. If the odds are exactly 50-50 that two randomly chosen students in the class will have blue eyes: How many students are in the class?