This is my take on the Very popular Robot Bob concept, i have modified the head and base to allow for easier assembly.
Please be aware i have not completed this project yet! although prints are coming along nicely!

12-01-2015
As requested my Bob Arduino files can now be downloaded, as a small disclaimer i hold no responsibililty if he takes over your house hold!!!

BOM
Arduino Nano V3.0
HC-SR04 Ping Sensor
4xAAA Bat pack.
Some Strip Board.
4x9G Servos
12x8mm On/Off switch
My build plan is to make a common rail GND and +6v from the strip board, this will feed all devices with power, The Aruino has mounts in the top of the head with a USB port hole, the HC-SR04 pushes through the eye holes, the Strip board will sit in between the 2 servos that come up though the base, and there is an on/off switch mount between the legs!.