Educational games and simulations can engage students in higher-level cognitive thinking, such as interpreting, analyzing, discovering, evaluating, acting, and problem solving. Recent technical advances in multiplayer, user-created virtual worlds have significantly expanded the capabilities of user interaction and development within these simulated worlds. This ability to develop and interact with your own simulated world offers many new and exciting educational possibilities. This article explores the technical capabilities and educational potential of these new worlds. Additionally, it presents and illustrates a model, which uses interaction combinations, to identify course content and topics having educational applications in virtual worlds. (Contains 6 figures.)