The LEGO Game, in collaboration with Google, presents a new Online CAD Software experiment.
At the moment, this software seems very simple, with a limited palette of bricks and colours.
The software requires a browser and any device with WebGL capabilities, that could be a Personal Computer, a Tablet, a Smartphone...
At the moment I tested it with Chrome, Firefox and Opera on a Personal Computer.
The peculiarity of this web application is that it has Social features: you can build your creations in a virtual LEGO word where your position is tracked by the GPS function of your device (if any).
Link: Build with Chrome.