Why not be official? The official Arduino Robot is a great way to learn about electronics, mechanics, and programming with no soldering required. It's a tiny computer on wheels that you can hack to perform all sorts of tasks. Just pop in the included color LCD screen, load up the Arduino IDE, plug in the USB cable, and you'll be ready to load any one of the included example programs. The robot comes with a number of integrated inputs, two potentiometers, five buttons, a digital compass, five floor sensors, and an SD card reader. It also has a speaker, two motors, and a color screen as outputs, and plenty of prototyping space and TinkerKit connectors for expansion. It even includes 4 rechargeable AA batteries and a charger.

The "brains" of the robot consists of two ATmega32u4 microcontrollers. If you're just getting started with electronics and programming, you should work with the Control Board. As you become more experienced, you may want to tinker with the Motor Board.