Thought I would post some pictures of my latest robot, Xr-B3. He is powered by an AVR ATMEGA324P micro controller on a custom board that I made. He is using an XBEE module to communicate with my PC (and eventually with other robots). Onboard sensory includes: 3 Sharp IR sensors (for wall following and obstacle detection), an SRF-05 sonar sensor and AVRcam. The sonar and camera are mounted in a 2-axis head. He also has quadrature encoders on each wheel, I currently have code implemented for closed loop turns and rolling forward a set distance, but have yet to do continuous speed control.
UPDATE: I've now gotten most of the mapping code working. He can make metric maps of small areas - or topological maps of larger areas. And in theory he can make topological maps from metric maps... but I've pretty near run out of memory to handle that - 2K of RAM only goes so far. I've added a pic below of the Map-Builder GUI (written in Python) which displays his map:
Here is B3 running through the Maze. This video doesn't show any backtracking (I'm still having issues with the transitions):
And, a quick video of B3 using his AVRcam to follow an object: