If you need a way to design a circuit or show a nice graphic of it for someone else to follow, you might consider Fritzing from fritzing.org.
A quote from their website:
Fritzing is an open-source hardware initiative that makes electronics accessible as a creative material for anyone. Fritzing.org offers a software tool, a community website and services in the spirit of Processing and Arduino, fostering a creative ecosystem that allows users to document their prototypes, share them with others, teach electronics in a classroom,and layout and manufacture professional pcbs.
Fritzing software is vector based so you can, drag and drop circuit components, easily re-size and attach wires.
It allows you to make COOL looking graphics like this:
The Fritzing software comes with an extensive libary of components, however there are others who have created libraries of parts too. One of my favorite Internet hangouts is Adafruit.com. They have created a Fritzing library of parts which you can find on Github here.