Geoffrey is approximately 3' tall.  His locomotion system consists of a 400 Series Roomba with the vacuum removed and controlled via serial commands through its SPI interface.  On top is a Yoostar webcam consisting of a 640x480 pixel camera and dual microphones.  Inside is an Acer One netbook that has a 1.6 ghz Atom processor, 1 gb of RAM, 160 gb of hard drive space, and built-in wifi.
Geoffrey runs custom Java software for control that uses the roombacomm and jinput libraries.  He was named "Geoffrey" by my girlfriend due to his long neck.  The bowtie is her idea too! (she rhinestoned the tie herself).
Geoffrey has software for both on-board remote mode (using a wireless XBox360 controller), and a telepresence mode that allows both movement control and speech synthesis.  He has an autonomous "bump and turn" mode, but it doesn't work quite well in real-world situations.

Here are some more links on how Geoffrey was made and how you can make your own.
Nerd Nite Presentation
How to Build a Roomba Bot
How to Remove the Vacuum From Your Roomba

Update - Source code for driving Roomba with XBox controller
Note - requires RoombaComm and JInput!


Skeleton Prototype Halloween
Outside Intergalactic Nemesis