Collecting parts and planning for my Arduino based "Start Here" robot.
Parts
Just a pile of parts so far. Arduino-compatible board for the brain (Seeeduino), motor controller shield (open source thing), Sharp IR sensor for obstacle detection, LCD status display. Have other parts on order : Solarbotics GM-9 motors plus wheels, servo for panning the IR sensor around.
Jan-20-2009
Got more parts in the mail today - GM9 gear motors, wheels, battery box, servo, some headers.
Now I've got some planning to do for the base, and how I am going to control servos and drive motors.
Great :)But i’d choose
Great 
But i’d choose standard Arduino Diecimila/Duemilanove and standard motor shield.
motor shield and processor board
The standard Arduino Diecimilia/Duemilanove are good boards, and have USB connectors. I was thinking about building the board from a kit (freeduino) then saw that the Seeeduino assembled was the same price as the Freeduino USB kit. One issue that I can see with the Seeeduino is that it will be difficult to replace parts if I blow up something. You can just pop in another cpu chip if you blow it out on the other Arduino boards.
I also have the Motor Shield kit, which is this design from the Arduino web site: http://www.arduino.cc/en/Main/ArduinoMotorShield
I think this motor shield will be fine for my current project. However upon further consideration, I think assembling the same motor control circuit on a protoshield PCB is a better choice - then you can put sockets for servos and sensors on the same board.
Thanks!
ps. I decided to use some 1/8 inch birch plywood for the chassis.