SUMO is a microscopic, multi-modal traffic simulation.
Modular System for Shelves and Coasts
An Open source Analysis and SImulation Toolbox for Fuel Cells
Multiscale Neuroscience and Systems Biology Simulator
Open source codes related to dissipative particle dynamics
realistic truck simulator with 3D graphics done from zero
realistic truck & car simulator, with OpenGL graphics
The educational lattice Boltzmann code
rp6simul is a simulator for the RP6 robot (AREXX Engineering)