Other
Chemical Reax/exothermic Reactions
A wonderfully complete primer on exothermic reactions in the context of chemical spills. Covers Reactions with Air or Water, Combustible Organics, Polymerization Reax, Decomposition, Corrosion, and much much more.
Florida State University
Florida State University: Atmospheric Composition
This page deals with the composition of the earth's first atmosphere and how it has changed. Also the elements and percentages that make up our current atmosphere are listed.