Science

Cornell Math & Science Gateway: An award-winning site for students in grades 9-12.
SciCentral: Science news and research for more advanced reference. Requires registration. Categories include Biological Sciences, Health, Physical & Chemical Sciences, Earth & Space Science, and Engineering. Great for reports.
The Science Page: Each link here is described to make your search more efficient. A great site with many links organized by discipline. There's a search engine on the home page.
Science Learning Network: A real mix of science sites for students and teachers. Each link is annotated. Check out the Top Ten.
Science NetLinks: This is part of the Marco Polo site--from MCI and the National Academy for the Advancement of Science. Once you choose a general science subject area, you can click on a grade level and choose a content area from a pull-down menu.
Brain Pop: This is a funny, noisy site. You can view short movies on health, science, and technology topics. The limit is two per day for non-members.
How Stuff Works: Find out how any number of inventions work--from squirt guns to nuclear power plants. There's even a section on how stuff will work in the future. If you can't find what you're looking for, or have a question you can't find the answer to, you can email your request to Marshall Brain, producer of this site (yes, that's his real name), and his talented staff.

Museum of Science, Boston: Online exhibits and descriptions of exhibits are featured here, along with 'Learn More' links to recommended science resources on the web.
National Air and Space Museum: "Looking at Earth" is an online version of the currently featured exhibit at the museum. Examples of satellite imagery and aerial photography display how remote sensing is used for urban planning, geology, archaeology, military reconnaissance, environmental monitoring and natural disaster assessment.
The Field Museum: Online exhibits and an 'ask a scientist' program are featured.
The Franklin Institute Online: Features exhibits about the human heart and circulation system, early fight, scientific instruments from the museum's collection, and weather. Information on careers in science is also offered.
Inventure Place: This is the National Inventors Hall of Fame. The site has links to invention sites, and invention competitions and awards.