Divide the Cake
This model is an extension of the Altruism model. It is based on Brian Skyrms's model from "The Evolution of the Social Contract." It shows how competing populations with different resource-use habits can stabilize under different viscosities and relative densities.
For detailed instructions on using the program, take a look at the info window from the Divide the Cake model.
Click on one of the pictures to see a quicktime movie of the model: