Georgia Dome  April 21st -> 23rd. Cost is $0!

http://www.usfirst.org/robotics/2005/chevents.htm

http://www.vexrobotics.com/index.php/first

Having taken a Masters degree in Robotics (+ AI) I will say don't expect too much from the entries. Robotics is VERY hard - to build a robot one needs patience for battling problems heuristically rather than using logic solving skills. A strong mathematical background helps too.