GNU Octave - GNU Octave is a programming language for scientific computing.
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
MATLAB - A high-level language and interactive environment for numerical computation, visualization, and programming
Solve Elec - Solve Elec is a free educational program to draw and analyze electrical circuits.
Xcos - Xcos is a graphical editor to design hybrid dynamical systems models.
Oregano - oregano - An electrical engineering tool for GNOME