The General Robotics, Automation, Sensing and Perception (GRASP) Laboratory at the University of Pennsylvania is developing algorithms to control swarms of quadrotors, also known as quadcopters or quadricopters.
Their research group has some amazing videos of quadrotors in coordinated flight, and quadrotors working together to perform a coordinated construction task. The GRASP lab is involved in numerous other projects that are worth checking out.
Here is a video of quadrotors in coordinated flight:
Here they perform a construction task:
The latter video was featured on The Colbert Report.
Amazing work (and a little creepy!)