2005 was named The World Year of Physics to coincide with the one-hundredth anniversary of three of Albert Einstein's groundbreaking discoveries. In 1905, Einstein proved the existence of atoms and molecules, validated the concepts of quantum mechanics, and developed the theory of special relativity: E=mc2. I chose the following sites because they are mix of serious homework help and physics fun.
This illustrated physics timeline tells five color-coded histories at once: cosmic, human, atomic scale, living world and technology. In addition to traversing the timeline event by event, you can skip around by decade, by using the index page, or with the drop-down search function. My favorite sections are the Arts & Culture sidebars you'll find on each decade page. "The references to Art woven into the bottom border serve as reminders that science is but one of many different perspectives on the world."
The creators of this site yearn to rid you of your fear of physics, and have created a "friendly, non-technical place for you to come and play with the laws of physics for a while." Best clicks are the animations and videos (such as "How Shaking Motion Can Destroy Structures" and "Hanging Bicycle Wheel Spinning" ) listed on the front page. The Homework Help section is reserved for paying members, but the rest of the site is free access.
Physics 2000 is a collection of more than sixty interactive applets and lessons demonstrating a variety of physics principles, and my pick-of-the-day site for high-school students and adults. I've always wanted to understand quantum mechanics (at least on a rudimentary level), so I immediately clicked on Quantum Atom (look under Science Trek) and found lots to learn and absorb. If you are looking for something specific, try the Table of Contents.
The Physics Classroom is an illustrated, animated tutorial for high-school physics students written by high-school physics teacher Tom Henderson. The site is divided into eleven chapters (such as Newton's Laws, Waves, and 1-D Kinematics) each containing lessons, quizzes, and multimedia demonstrations. If you want to jump directly to the animations, they are listed separately in the Multimedia Physics Studio menu.
Physics.org is a specialized physics search engine, and a multimedia playground showing physics in everyday items. To use the search engine, enter your age, your level of physics background, and an natural language query such as "Why is the sky blue?" If you register (it's free) Physics.org will remember your settings. Don't leave without visiting Physics Life (animations of physics in common household items ) or Physics Evolution (an interactive map showing the history of related physics ideas.)