DesignSpark PCB is described as 'The World’s Most Powerful Free Schematic and PCB Layout' and is an app in the Education & Reference category. There are more than 25 alternatives to DesignSpark PCB 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 DesignSpark PCB are Fritzing (Paid, Open Source), QUCS (Free, Open Source), LibrePCB (Free, Open Source) and Autodesk EAGLE (Free Personal).
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.
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.