Created by students, this site links you to whatever you need to know -- from American history to zoology. It's organized by topics based on school curricula, so you can access hundreds of helpful sites. Topics include weather, geology, astronomy and computers. If you're a future historian, or just trying to pass a history class, you'll be glad to hear that the history sections are particulary strong.
The site promises to remove dead links promptly, so you shouldn't waste too much time here. There are also links to Encarta and the Canadian Encyclopedia site.