Note: While it's still up, a much more detailed account is here: http://www.wikihost.org/w/crackrobot/
Over the summer of 2008, I was awarded a Small Undergraduate Research Fellowship to work on a new type of climbing robot. Utilizing cam-like end-effectors, the robot is able to climb up cracks and hang from a wall without actively using power. The electronics were from a Vex Robotics kit and the mechanical parts were all made by me.
The first real attempt (after a proof-of-concept using the Vex links) was able to climb parallel-sided cracks.
The next version was intended to be able to climb cracks that do not just go straight up-and-down. An infrared rangefinder scans ahead of the front arm, detecting the largest gain and dropoff in distance. The front arm pivots accordingly. The video below shows this process on a test rig. Unfortunately, the summer ran out before this part could be completed.