Here are some sites containing related material that may be of interest.
Annotated Bibliography on the Evolution of Cooperation- Just as the title says. Prepared by Robert Axelrod of the Iterated Prisoner Dilemma fame
Chaos, cheating and cooperation: potential solutions to the Prisoner's Dilemma- A well designed site with information primarily about the Iterated Prisoner's Dilemma (model 2). Includes some good biological references and some other links.
The Primordial Soup Kitchen- An award winning site about with great pictures and hands-on demonstration of spatial models.
Prisoner's Dilemma- Learn about the Prisoner's Dilemma and play against the computer.
The Prisoner's Dilemma at Principia Cybernetica Web- Some encyclopedia information about the Prisoner's Dilemma.
Prisoner's Dilemma Sources- More references about the Prisoner's Dilemma.