This guy has posted a ton of screencast tutorial videos for math and physics. Chemistry teachers may want to reference these to help students with their basic skills.
This includes resources for Pre-K through 12 for all subject areas. You may want to take a look to see what is offered for science and upper grade levels.
You'll find a lot on this site, including a large number of resources, textbook reviews, powerpoint tips, tutorials, templates, resources for multimedia approaches for teaching biology, etc. Be sure to click on the About tab along the top of the page for additional information and the purpose of this bioblog. Great stuff.