The best definition of Game Theory I've seen is contained in the Economists "Dictionary of Economics". In part it states:
- Much of economic theory is concerned with the process and conditions under which individuals or firms maximize their own benefits or minimize their own costs in markets in which their individual actions do not materially influence others (perfect competition). There are, however, many cases in which economic decisions are made in situations of conflict, where one party's actions induces a reaction from others. An example is wage bargaining between employers and unions. A more simple case is the of duopoly, in which the price set by one seller will be based on his view of that set by the other in reply. The mathematical theory of games has been applied to economics to help elucidate problems of this kind.
- Game theory studies strategic interaction in competitive and cooperative environments. Only fifty years old, it has already revolutionized economics, and is spreading rapidly to a wide variety of fields. It develops general mathematical formulas and algorithms to identify optimal strategies and to predict the outcome of interactions.
The Economics site at About.com keeps a list of resources on game theory called simply "Game Theory Resources".

