help with aparallax ultrasonic distance sensor on arduino

I found some sample code on arduino.cc  search for ping ultrasonic sensor and you'll find a ping and l.e.d. example. I used it to interface the ping to the motor driver and arduino. hope this helps.

DOn't know Arduino, but somethiing like :

if (ultrasoundValue < presetDistance ) then GoTheOtherDirection

might be a start. 

Just relate what distance to an objact you feel is safe for the robot to get within, then use that value to change what the robot is doing. You mihgt have code that sets the robot going forward initially, andin its travels, the distance measured to obstacles starts getting smaller. So you would have a set value to trigger the robot to either turn away, or even back away from the detected whatever.