A math website with over 3,200 mini-lessons and examples, from prealgebra to differential equations.
The webpage for National Geographic--containing articles and images on animals, the environment, travel, adventure and much more!
This interactive periodic table lets you find information on any of the 118 elements, the chemistry behind them and a whole lot of other science-related stuff.
Founded for the "increase and diffuciton of knowledge", the Smithsonian Institution's website contains a wealth of articles, collections, exhibits and even an encyclopedia.
Math lessons and a math calculator--enter what you need to know or what you need calculated, and Wolfram Alpha will help you find the answer.