This is my first robot, it simply avoids obstacles by using an ultrasonic sensor. It uses an Arduino as its brain, a pair of DC motors for locomotion and a small servo for swinging its sensor around.
Looking back on how I entered the world of robotics, I wished that I had a sturdy, easy to program Arduino shield and platform. Well, I made what I wished I had. It turned out to be my best looking robot ever! I made the shield in Fritzing (to attach to the Arduino Uno and the robot). The PCB image is attached (it is double sided, the darker wires are on the bottom). I know I have some empty space and rough edges on the pcb, but it still works flawlessly. I will create a library for the functions of the shield, greatly simplifying the programming aspect.
Well, finally I've started to assemble my first go at building an autonomous bot, nothing fancy, nothing original just something to learn the ropes. I'm going for a 2WD design that to me seems to be quite ubiquitous.
As of the moment (May, 17th 2012) basically I've only glued together a couple of DVDs (following generalgeek's sugestion) to use as base, and then also hot-glued a couple of DC motors and a 3rd non-motor wheel to it.
Component-wise I'm only waiting for a couple of transistors to build an H-bridge (as sugested on a Dan M's post).