Google - Research database allows searching of the scholarly literature.
J. Park, ChemTeam - An excellent tutorial on balancing reactions and reaction types, including practice problems.
Virginia Tech Chemistry Department - Equations show chemistry in action.
IrYdium Project, Carnegie Mellon - Java applet displays mole and mass changes in a chemical reaction.
G. Sibert, Roanoke Valley Governor's School - Exercise in balancing chemical equations.
U. Liverpool - Quiz about chemical reactions.
An alphabetical glossary of relevant scientific terms.
Y. L. Wong, Wake Forest U. - Interactive exercise details equation balancing.