Science

Learner.org , hosted by Annenberg Media, offers video tutorials on many academic subjects including science. Although the site is designed as a teacher's aid, it's a useful resource for the layman, too. There are videos on a number of science topics for students in kindergarten through high school. A free registration is required to view the videos.

Physics.org is a comprehensive site run by the Institute of Physics. Its extensive database includes links to over 7,000 recommended sites, news articles, education and career advice, and interactive physics games. Registering with Physics.org allows you to customize your search results based on your age and level of knowledge.

The Physics Classroom is a multi-part tutorial designed for high schools students and written by a high school physics teacher. In the "Physics Tutorial," you'll find written lessons and quizzes to test your comprehension. Or if you need a visual to better grasp the concepts, the "Multimedia Physics Studio" provides animations to help you better understand the basics. The "Physics Help" section has practice problems that test your comprehension.

Conceptual Physics , by Paul Hewitt, is a textbook used by many high school classes. This companion Web site can be used on its own or to supplement the textbook. It features summaries of topics, a Q&A section with Paul Hewitt, and valuable links to other sites. Each link is organized by specific topic and accompanied by an informative description, so you know what to expect.

General Chemistry Online is managed by a college professor and focuses on high school-level chemistry. It features tutorials, lecture notes, quizzes, exam guides, interactive experiments, and a helpful FAQ section. Of particular note are the tools that the site offers: the "Construction Kits" help you to build chemical equations, ionic compound formulas, and do unit conversion problems; and in the "Toolbox" section, you'll find a "GraphPad" that builds a graph from the data you enter and e-mails it to you as a GIF file.

The University of North Carolina-Chapel Hill Chemistry Fundamentals Program is designed to help college freshmen prepare for college-level chemistry classes. It reviews lessons from high school and introduces concepts that will be learned in college classes. Useful for both high school and college students, this site will help you master the fundamentals of chemistry.

The Howard Hughes Medical Institute's BioInteractive site has a great depth of topics on human biology. Most topics include Web casts of related lectures, explanations, videos, and articles. A great feature of this site is the  "Virtual Labs" section. You'll need to download Shockwave, but it's worth it. You'll get a unique perspective: for instance, in the cardiology lab you're an intern assisting a doctor in examining and diagnosing three different cardiac patients.

The Biology Project , created at the University of Arizona, is an interactive resource for high school and college biology students. There are many well-organized subjects with explanations, illustrations, and problem sets. Each topic provides related links, and several of the topics are available in Portuguese, Spanish, or Italian.