MATLAB - A high-level language and interactive environment for numerical computation, visualization, and programming

Circuit Simulator - Animated electronic circuit simulator using ideal components to visualize voltage and current.

Wolfram Mathematica - Mathematica has characterized the cutting edge in specialized processing—and gave the chief calculation environment to a large number of pioneers, instructors, understudies, and others around the globe.

iCircuit - Its advanced simulation engine can handle both analog and digital circuits and features realtime...

GNU Octave - GNU Octave is a programming language for scientific computing.

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.