Cover the earth

LightningMaps displays near real-time lighting strikes around the world, compiling data gathered from a network of volunteers using low-cost detectors. Fire it up when a storm's coming, and observe the fireworks from above. If you zoom in far enough, the map will show the expanding sound wave from each strike, like ripples in a pond.   

There are places online that have begun to feel like collaborative demonstration projects in the tragedy of the commons, but this is an example of technology enabling a massive, distributed project that wouldn't have been possible only a few years earlier.