http://www.e-missions.net/
This website is absolutly amazing. It has many simulations that are very interesting. They range from making whether predictions to trying to calculate which part of the moon needs to be evacuated because a comet is going to hit it, to finding a place on Mars where a base could be built. This website is great because all of these simulations satisfy the NCTM standards. Definitely a great way to interest the students and motivate them to learn. The only thing that is negative is however, that this website is more geared toward middle school math and science, but there are 2 simulations that can be used in highschool.