Mojang, together with Code.org, revealed an interesting initiative to teach programing via Minecraft. This is not the retail version of the game, but a rather minimalist variant, and it proposes a series of challenges to the player in a browser-based version of the game. To solve them the player will join lines of code and then execute commands.
It's actually very simple, and it's presented in a clear and concise format. It's free and takes an average of an hour, and in the end the player is presented with the results of their efforts. If you have any curiosity regarding how the basics of programming work, this might well be worth a look.
You can experience the mini-game here.