Betocracy is a predictive market system. By "buy and selling" shares -- no money involved -- various alternative outcomes can be weighted. So, for example, if you wanted to predict the outcome of the next three basketball games, students could trade shares such that the own shares in the alternative they believe is most likely. Naturally, the more popular picks are the most valuable/expensive. This is a great system for learning about markets and economies. The system is in beta, but that does not stop you from testing it out now.