FlightGear Flight Simulator: free open-source multiplatform flight sim
A minimalistic digital logic simulator
An advanced network simulator to design and configure virtual networks
A network server for the flightgear simulator
physics-based multicellular simulator
Simulator for medical emergency departments
turn-based wargame/simulator
PySCeS is the Python Simulator of Cellular Systems
A wireless push-type network simulator.
Modbus slave simulator
A simulator for biological and physiological models
A software gps simulator
NeuralSyns is a neural simulator for large spiking networks.
The Future of the Java Circuit Simulator
A tool able to simulate gene-environment and gene-gene interactions.