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.

LabVIEW - LabVIEW offers many of the functions you'd find in a traditional script-based programming language presented in a more intuitive visual interface ideal fo engineering.

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

myOpenLab - MyOpenLab is a platform for finished elements (program components) that can be linked together.

Solve Elec - Solve Elec is a free educational program to draw and analyze electrical circuits.

PyLab_Works - PyLab_Works is a free and open source replacement for LabView + MatLab, written in pure Python.