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.
Pspice - OrCAD PSpice technology provides the best, high-performance circuit simulation to analyze and refine your circuits, components, and parameters before committing to layout and fabrication
Proteus PCB design - Proteus PCB design combines the schematic capture and ARES PCB layout programs to provide a...
QUCS - Qucs, briefly for Quite Universal Circuit Simulator, is an integrated circuit simulator which means you are able to setup a circuit with a graphical user interface (GUI) and simulate the large-signal, small-signal and noise behaviour of the circuit.
HSPICE - As IC geometries continue to shrink, the need for an accurate circuit simulator is critical.
MacSpice - Electronic circuit simulation for the Mac, support and downloads site.