"HippoCampus is a project of the Monterey Institute for Technology and Education (MITE). The goal of HippoCampus is to provide high-quality, multimedia content on general education subjects to high school and college students free of charge."
HippoCampus would be a valuable addition to a classroom or for students who are interested in taking their learning a step further. Teachers can use the site as a supplement to their teaching or create a Custom HippCampus page for their students. Several screenshots are available to showcase what the website looks like and how students can interact with the software. There are several valuable lessons free of charge for teachers. I could see this being used on days that teachers had a substitute teacher as well.
Check it out and see if any of your classes are available.