HippoCampus has homework and study help for math, including algebra and calculus, science, including biology and physics, U.S. History, government, and a few other topics. This website is great because it teaches you what you need to know through text and video. It covers many, many topics in short, easy to handle snippets. There are also many subtopics under the main topics. It would be a great place to look for project or report topics for class.
I recommend this site for students from middle school all the way up to college. I have caught myself using it to refresh my memory on some history and math subjects. I also like that it does not look like a kiddie site. The website was created by the Monterey Institute for Technology and Education (MITE). Their goal is to create and support an educational website that is no cost for its users (free). Want to impress a teacher? Share the site with him or her and your classmates.
Website; 12+; Monterey Institute for Technology and Education (MITE); http://www.hippocampus.org/