EcosimPro - EcosimPro is a continuous and discrete modelling and simulation software.
FlexSim - Simulation software to model, simulate, predict, and visualize systems in manufacturing, material handling, healthcare, warehousing, mining, etc.
E-Hub - Simulation Modeling
ns-3 - a discrete-event network simulator for internet systems
Uber Cloud - UberCloud is the cloud for engineers that provides cloud simulation solutions for engineers and scientists.
Paessler Multi Server Simulator - Paessler Multi Server Simulator is inexpensive and robust software that helps you power massive-scale testing.