A little over a week ago I posted a brief article and video about the thousand robot swarm developed at the Harvard School of Engineering and Applied Sciences. SEAS worked on this project in collaboration with Harvard's Wyss Institute for Biologically Inspired Engineering. The Wyss Institute's website has a fascinating collection of articles and videos about their work.
Three videos in particular are worth watching if the details of cheap, swarming robots interest you. They describe how the Kilobots work, and give a clear demonstration of their capabilities, along with brief explanatory articles:
Remarkable work is taking place in the field of biologically inspired robotics, and if you want to follow the state of the art, bookmarking the Wyss Institute site would be a good first start.