Proteus PCB design is described as 'combines the schematic capture and ARES PCB layout programs to provide a powerful, integrated and easy to use suite of tools for professional PCB Design' and is an app in the Education & Reference category. There are more than 25 alternatives to Proteus PCB design for a variety of platforms, including Windows, Linux, Mac, Online / Web-based and Android. The best alternative is KiCad, which is both free and Open Source. Other great apps like Proteus PCB design are Fritzing (Paid, Open Source), Autodesk EAGLE (Free Personal), QUCS (Free, Open Source) and LibrePCB (Free, Open Source).
The Quite Universal Circuit Simulator (QUCS) is an integrated circuit simulator allowing the simulation and graphical presentation of results of large-signal, small-signal and noise behavior in circuits.
KTechLab is an IDE for microcontrollers and electronics. It supports circuit simulation, program development for microcontrollers and simulating the programmed microcontroller together with its application circuit.
The gEDA project has produced and continues working on a full GPL'd suite and toolkit of Electronic Design Automation tools. These tools are used for electrical circuit design, schematic capture, simulation, prototyping, and production.