Like the magnetic field demonstrator set and Galton Board probability machine before it, I've got another educational-tool-slash-awesome-desk-toy for you: the SunnyTech ST05, which is a magnetically levitated, solar powered electric motor (aka "mendocino motor").

If you've never seen one of these, it's a pretty neat mixture of magic and physics:

The motor consists of a spinning shaft that is held up by repelling magnets, stabilized by resting a point against a wall. It is powered by solar panels mounted on the spinning shaft, which generate currents through coils of insulated wire.

Watch an example of a mendocino motor here:

While the energy output of this type of motor is really quite low, it's still great for sparking a kid's interest in science, and it just looks cool besides. It doesn't take much light to get the thing to spin; it works on cloudy days nearly as well as sunny ones (where it'll top out at 1,000 RPM), or you can even shine your phone's flashlight on it.

The basic ST05 motor kit is $37 on Amazon. They also offer a version with a side propeller (model ST41) for $46.