Fritzing

Fritzing is an open-source electronic design tool focusing on makers, hobbyists, and everyone else interested in getting creative with interactive electronics. Document your electronic sketches, learn from example projects, produce your own PCBs, and share with the community. Fritzing differs from other tools through:

• A real-world breadboard view that is hands-on and easy to understand
• A visual component library including the Arduino, Raspberry Pi, SparkFun parts and many more
• An intuitive user interface, with seamless switching between breadboard, schematic and pcb design

The lively community on fritzing.org exchanges projects and tips, and there is also a PCB service "Fritzing Fab" that produces user designs.