Construction toys are always good for kids both big or small. Cubelets from Modular Robots is a set of magnetic and modular building blocks that can be built into robots that respond to the world around them. Using sensor, logic and actuating blocks, you can build robots that drive around on a tabletop, respond to light, sound, and temperature with no programming or wires. There are currently 15 Cubelets, including Battery, Brightness, Distance, Drive, Flashlight, Inverse, Knob, Rotate, Speaker, and Temperature.
Recently funded by a venture capital investment, they can be ordered for $160 for a set of 6 (1 drive, 1 flashlight, 1 brightness, 1 distance, 1 battery and 1 passive), or get a 10% discount when you buy in bulk with 10 sets for $144 each.