Atomic structure
Chem4Kids - Atom Basics
Atomic Structure - introduction to periodic table is good, the rest is best left for university
Ionic Compounds
Polyatomic ions
Molecular Compounds
Acid-Base Reactions
Wisc-Online Acid-Base Reactions
Resources
VisionLearning - whole chemistry course
Naming Compounds
Aus-E-Tute - Awsome site for chemistry tutorials for highschool
Chemical Reaction Worksheets
Chemical Reactions - with activities, labs and links.
Naming Polyatomic Ions
Biology
- Cell cycle
- Cell specialization
- Organs and systems
Earth Sciences
Climate change - greenhouse effects - carbon cycle
Physics
Optics
Introductory book on physics. An OK section on reflections and refraction
Optics4Kids Not as deep as the above, but a better intro to concepts, plus interactives and experiments.