The SolarSpeeder 2 Kit is a very quick Solaroller that can cover 3 meters (10 feet) in under 40 seconds in direct sunlight.
This is a super simple solar-powered dragster. All it takes is a bit of basic soldering to install a few components, and then you're all set. The SolarSpeeder will sit in the light (sunlight works best!), and when it's all charged up, it'll shoot off in a line. The SolarSpeeder uses fancy MillerEngine Technology, which means there's a big improvement in performance with no increase in complexity or cost.
This is a perfect introduction to electronics, with a detailed manual (lots of pictures and step-by-step instructions) that will walk you through how to solder and install each component.