circuits.io
From circuits.io: "Circuits.io was founded in 2012 by Karel Bruneel and Benjamin Schrauwen. After struggling for years to design and teach to design electronics using existing EDA tool, they felt that electronics design needed an urgent jolt. Learning from how software is designed, they came up with the following magic recipe which is at the heart of circuits.io: (i) allow to easily build on pre-designed electronics modules, (ii) use intuitive tools that hide much of the complexity in software, and (iii) embrace the open hardware movement. Furthermore, we will soon allow easy PCB ordering right from circuits.io, no more messing with Gerber files. We promise that circuits.io will always be free for open hardware designs and that you can export all your designs, we will never lock in what actually is yours."