If you want to avoid fire, malfunction, and other accidents, it would be nice to design a circuit before you start soldering. CircuitLab's free web application is a free, web-based tool that can simplify this process: we simply place resistors, capacitors, current sources and other circuit details on the drawing board and put it all together. The creators say that you can also model how your project will behave, and if you have problems, you can turn to the community for help by sharing your schemes, marking them as public. In addition, since the application is web-based, it should work well on all platforms.