Most feather weights have the same stuff in them as other robots, they have motors with a reduction gear box (makes the spinning slower, and gives it more force), going to a wheel or wheels, and then a speed controller connects the motors to the battery and receiver.
Often motors out of cordless drills are used, because they all ready come with the right reduction, and you can buy wheels that fit straight to their shafts. Or you could use the gimpson motors, which are thought to be stronger than the drill motors. The wheels can be found either on the robo challenge website, or the gimpson website. For Speed controllers (also know as ESC's) people often use electronises (simple and rugged), sabertooths (versatile but slightly weakly made), scorpions (half way inbetween the other two esc's), or some others. And for construction materials, HDPE (a strong type of plastic) is often used, as it's easy to machine because it can be cut with wood saws, and screws together with wood screws. And I think you already have a radio control system, from your servo powered ant (unless it's the wrong type)
Hope this helps.

Edit:you beat me to it!