CometCAD is described as 'Circuit schematic and layout editor program for Windows 2k, XP, Vista and 7' and is an app in the Education & Reference category. There are more than 25 alternatives to CometCAD for a variety of platforms, including Windows, Mac, Linux, Online / Web-based and iPhone. The best alternative is KiCad, which is both free and Open Source. Other great apps like CometCAD are Fritzing (Paid, Open Source), LibrePCB (Free, Open Source), Autodesk EAGLE (Free Personal) and OrCAD (All Products) (Paid).
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.