Currently on week two of a robot project featuring an Arduino and Xbees for communication.
Wrote control software in C#/Mono (works in linux & windows) that controls the arduino remotely. The motor driver and motors are all set up. Planning on ordering some OD green UHMW plastic from an online store sometime next week. Then it's body building time :)
For the main sensors i'm thinking two independent Sharp IR sensors and wayyy down the road a tiny B&W camera.