This page has a long listing of Wiki examples for all subject areas. There are a good number of science example. An easy way to find them is to Click on Edit->Find, type in Science, and keeping hitting enter (or find) to get through the page.
Mr. Noon, a science teacher from upstate NY, has his classes online. Beware - this is a loud website. Watch the Flash animation in the PSP to get to the "Enter" button. He has some cool stuff for his classes and in general. This has resources for a lot of our sciences.
This was posted to the Science Teachers group - For those that are not members, here you go! Great resources for chemistry related simulations - also contains some biology related chemical simulations as well (i.e. protein structure)
This is a exciting. The open learning initiative (Carngie Mellon) offers open and free courses in the areas of math and science, more specifically chemistry, modern biology, and physics. "Take a look inside" to see the information presented. Interesting approach.
This has "science interactives", or virutal manipulatives that students can use. I've seen the roller coaster before, but I haven't seen the rest. Their new interactives include DNA, Periodic Table, Dynamic Earth, and the Rock Cycle.
Free textbooks online - I just took a quick look through, but they have bio, chem, physics, and biochem books for science. Scroll down on the page to find.
I just got friended in Diigo from someone who had this site bookmarked. Very cool stuff for science, especially chemistry. I love this guy's personality. Very entertaining!