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
Altair Activate - Altair Activate is an open & flexible tool for rapidly modeling and simulating products as multi-disciplinary systems in the form of 1D models (expressed as signal-based or physical block diagrams), optionally coupled to 3D models.
Oregano - oregano - An electrical engineering tool for GNOME
MATLAB - A high-level language and interactive environment for numerical computation, visualization, and programming
PCBWeb - PCBWeb is a 100% free Windows desktop CAD application for designing and manufacturing electronics...
Xcos - Xcos is a graphical editor to design hybrid dynamical systems models.