CircuitLogix - CircuitLogix electronics lab simulation provides fast, powerful schematic design and simulation in one complete program.

GNS3 - GNS3 is a graphical network simulator that allows simulation of complex networks.

LTspice - LTspice® is a high performance SPICE simulation software, schematic capture and waveform viewer with enhancements and models for easing the simulation of analog circuits.

ns-3 - a discrete-event network simulator for internet systems

Multisim - Multisim is industry standard SPICE simulation and circuit design software for analog, digital, and power electronics in education and research.

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.