RubyQuiz is a game played on the Ruby mailing lists to test your programming ability. Each week, a new quiz is posted, presenting some interesting problem to be solved. These problems are usually hypothetical problems, but every now and then a practical problem pops up. Even if you can't complete the quizzes, reading other's solutions and the commentary alone can make you a better programmer.
This week's challenge is similar to a game of battleship. There's a shape in a 10x10 grid. You have to write a program that first finds this shape, then maps out the shape with the least number of queries into the 10x10 grid.
There are two sites for RubyQuiz. The old site archives all of the challenges up to #156. All newer challenges are on the new site, up to the current challenge #211.