Understanding Science is a very cool site developed by the University of California Museum of Paleontology in collaboration with other partners, including Berkeley.
The site describes what science is, what is science evidence, how science works, why science matters, science and society and has a science toolkit. It does a very good job of explaining science and why we need to understand science (and how to understand it).
One of the really great pages is The Real Process of Science which is a much better explanation of how to conduct science inquiry than the Scientific Method. It talks about scientific evidence, exploration and discovery, and testing ideas. This is a much better way to accurately describe how science works than the scientific method.
There is a page for Teachers, which has teaching tips, science tips, and teaching science tips for grades K-16, separated by K-2, 3-5, 6-8, 9-12 and 13-16. The tips include implications for instruction, characteristics of students in each grade level, and ways to introduce and explain science.
There is also a Resource Library, which contains articles and links on teaching science, what is science, and much more.
This is a great site for all teachers and students, including teachers who are not "science teachers" but must teach science, such as elementary teachers.