NetSim - NetSim software was created to simulate various Cisco systems. Cisco software is known around the world as being one of the best network, routing and switch systems for businesses and private use. Read more about NetSim.
GNS3 - GNS3 is a graphical network simulator that allows simulation of complex networks.
slm - Slim, Jade like template engine for node
ns-3 - a discrete-event network simulator for internet systems
FlexSim - Simulation software to model, simulate, predict, and visualize systems in manufacturing, material handling, healthcare, warehousing, mining, etc.
OpenModelica - OpenModelica – A Free Modelica Environment!