I'd agree with the comments about K-9. It'd be a cool addition to the project to create an outer case similar to K-9, if you're a fan of the show.
That is a good idea and I will definitely consider doing that, however I would like to get the robot working before I work on the aesthetics.
I have made some progress on the robot and have been able to etch and solder two of the PCBs for the robot. The first one pictured is a voltage regulator circuit, and the second is a relay board that will allow the processor to interface to the motors.
The voltage regulator is a LP3852 low dropout linear voltage regulator. With a price of four dollars it is not cheap, however its characteristics made it extremely desirable for use in the robot. One of the features that makes is valuable is the fact that the dropout voltage is only about 250mV when driving a 1.5A load, allowing me to use the 6V batteries I was planing on using in the robot.
I also learned something new about relays, and unfortunately I learned it the hard way. When selecting relays, I tried to find some that was both cheap and would not require a lot of current to drive. After I found some that seemed adequate, I constructed the PCB and soldered the relays only to find that the relays would not activate. After checking the data sheet for the relays I found that they was described as a high efficiency relays. I did some reading online and found that some high efficiency relays use permanent magnets to make it easier for them to switch and are therefore polarized. I was then able to modify the PCB to fix the polarity issue with the relays.