ReMaze is a small Flash game which has some fascinating puzzles to stimulate problem-solving, and which is really quite engaging. This is well worth a look.

My only concern about a game such as this for education is that too often while I was dimly aware of the sort of strategy I should employ to solve the puzzles, I was too often relying on trial and error to solve the problems. To convert this into a thorough educational game would require careful thought about how to make the problem-solving more explicit.

Apparently there are 21 levels!