Read more at http://www.botjunkie.com/ and http://people.csail.mit.edu/jamesm/swarm.php.
Swarm-bots finding a path
MIT's James McLurkin: Swarm Robotics
A Swarm of One Thousand Robots
Termite robots build castles with no human help
Robots with a mind of their own
SWARM bot at Maker faire 2008