Multi-Physics Simulation System » http://smirnov.mae.wvu.edu/mulphys/
open dynamics engine (ODE) » http://opende.sourceforge.net/
Modelica
Analogue Dynamics Engine: The ADE is a physics engine constructed from a hybrid, analogue and digital, computer.
efg's simulation and modelling pages; http://homepages.borland.com/efg2lab/Library/SimulationAndModeling.htm
modeling high level cognitive processes http://cogent.psyc.bbk.ac.uk/book/
see also: Artificial Life, Evolutionary Robotics, Simulated Physics