Here is an interesting find:
Prisoners’ Dilemma is a game which has been and continues to be studied by people in a variety of disciplines, ranging from biology through sociology and public policy. Among its interesting characteristics are that it is a “non-zero-sum”game: the best strategy for a given player is often one that increases the payoff to one’s partner as well. It has also been shown that there is no single “best” strategy: how to maximize one’s own payoff depends on the strategy adopted by one’s partner. Serendip uses a particular strategy (called “tit for tat”) which is believed to be optimal under the widest possible set of partner strategies.
There is an online version here: http://serendip.brynmawr.edu/bb/pd.html