Fritzing

Fritzing is an open source hardware software tool allowing users to document their prototypes, and layout and manufacture professional pcbs.

Don't use Fritzing
Fritzing no equal for creating images of breadboard circuits. However:
 * New parts cannot be created from scratch within Fritzing, Inkscape or another vector design program has to be used.
 * Circuits are designed via a 0.1" pin pitch breadboard representation, and the schematic is created from that.
 * The schematic is ugly.
 * There are no nets or buses in the schematic view. Parts are connected by wires between individual pins. Connections cannot be named.
 * It is unlike every other schematic capture application on the planet.