Virtual Breadboard
Pspice
Oregano
BlackBoard Circuit Designer
Solve Elec
PCBWeb
Circuit Simulator
PCB Wizard
Multisim
LTspice
QUCS
EasyEDA
Proteus PCB design
KiCad
Pspice
Altium Designer
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
LTspice - LTspiceยฎ is a high performance SPICE simulation software, schematic capture and waveform viewer with enhancements and models for easing the simulation of analog circuits.
Oregano - oregano - An electrical engineering tool for GNOME
QUCS - Qucs, briefly for Quite Universal Circuit Simulator, is an integrated circuit simulator which means you are able to setup a circuit with a graphical user interface (GUI) and simulate the large-signal, small-signal and noise behaviour of the circuit.
BlackBoard Circuit Designer - Help building prototypes on so called breadboards easily
EasyEDA - EasyEDA - Web-based EDA suite; runs in browser.