KiCad - A Cross Platform and Open Source Electronics Design Automation Suite
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.
Altium Designer - PCB Design Software
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
LibrePCB - LibrePCB is a free EDA software to develop printed circuit boards.
Proteus - Proteus - Proteus is a great electrical suite for circuit simulation purposes. You can simulate a single processor or multiple ones at the same time. The application is a great alternative for Virtual System Modelling.