This is last years information, but I ran accros a reference, and do not remember seeing anything about it here. 40 minute video. Would be fun to have one of those PR2 robots to play with!
Google I/O 2011: Cloud Robotics
The talk mentioned being able to use ROS with Arduino, so I looking up this information:
Not enough to be able to build a complete bot running ROS on an Arduino, but enough to make it easy to use Arduino as part of a bigger system using ROS. A much more complete implementation will run on Andriod [in Java].