I think I mentioned that I went to a Minecraft session a couple days ago. It only works on computers at the moment but it could be used in a math classroom. It can be rather addicting. I started playing the tutorial and when they froze it after 20 min so they could give us information, I just about jumped out of my chair to strangle them because I was really into it. During the session, I came out with the question of how is it used in Math. The representative for the game gave me a link to a page with lesson plans. Most of these lesson plans seem to be for the age group of 7 to 12 but if I make it an after school activity, I could adjust a few things for my students.
The biggest thing I see about Minecraft is that it teaches perseverance, problem solving, and planning. This costs a bit but its not a huge amount.
While looking up things about Minecraft, I discovered there is something called Qcraft which teaches quantum mechanics and is free. It works in the Minecraft world. Once the school has Minecraft, I want to download Qcraft so that I can play with it.