Extra-Curricular Resources for Students?

rende asks: "With school soon starting or having already started for many, this seems like a timely question. The MIT OpenCourseWare project is looking like a great resource for additional information to supplement my own coursework this year. I was very delighted to find this information freely available online, and wish I would have known about it previously. I would like to ask Slashdot: Are there any other resources, offered by other schools or independent sites, that offer such a robust selection of information that would fit in nicely, with the standard classes of a science related major?"