Edheads is an interactive website that aims to help students learn through educational games and activities designed to meet state and national standards. The topics are science-based (brain surgery, weather, etc.) But are very well designed and engaging for Middle and High School students. The site is free and is well worth a look.
Awesome Science Teacher Resources- Chemistry Tab includes: study of matter, atoms, periodic table, compounds, chemical reactions, kinetic theory, gas laws, chemical quantities,acids and bases, nuclear chemistry, forensics, etc. Materials include: Activities and worksheets Laboratory exercises Links to useful pages Puzzles, games, and songs Online test reviews by topic