I found this site when looking for ideas to use in an upcoming demo/lesson about chemical and physical properties/changes. I guess there are only 25 experiments listed currently, but it gave me some good ideas to potentially use!
This site has various resources for elementary, middle and high school grades. Something especially interesting is the free video series titled "Women Are Scientists."
The Art Institute of Chicago's site has lesson plans, student projects, and other resources that connect art to science, which I really like. Again, another way to make science relevant to students!
This website has an interactive/clickable periodic table that shows photos, wikipedia articles, and podcasts (which are actually pretty neat) for each element.