NASA for high school students http://www.nasa.gov/audience/forstudents/9-12/features/index.html
Basic physics info such as motion, heat, electricity, light, and other topics. http://www.physics4kids.com/
Practice Balancing Chemical Equations with ChemBalancer. Try easy problems by clicking Classic Chembalancer or tougher problems with Brain Boggle Chembalancer. http://www.funbasedlearning.com
Get help with basic chemistry concepts http://www.chemtutor.com
Help with basic physics concepts http://www.fearofphysics.com
Help with basic physics concepts http://www.physicsclassroom.com
This website has several games centered around the elements on the periodic table. Click on "games" then play around. http://education.jlab.org/
Practice with writing and naming of compounds with polyatomic ions. http://www.wisc-online.com/objects/index_tj.asp?objID=GCH3304
More polyatomic ion help http://dbhs.wvusd.k12.ca.us/webdocs/Nomenclature/Polyatomic-FormulatoName.html
Quiz yourself over writing chemical formulas with polyatomic ions http://www.syvum.com/cgi/online/serve.cgi/members/gillilandd/quizzes/polyatomic.tdf
Play a matching game to help figure out names and formulas for compounds http://www.quia.com/mc/65800.html
Fizzics Fizzle offers interactive help on various Physics topics with varying degrees of difficulty. http://library.thinkquest.org/16600/
Practice identifying simple and compound machines and understanding how they work. http://www.edheads.org/activities/simple-machines/
National Geographic http://www.nationalgeographic.com