Modular Robotics has released a new product which goes by the name Moss.
Essential, Moss is a series of cube-shaped components which attach with small, spherical magnets.
To build a robot, simply connect a power supply to sensors and add additional parts, like a Bluetooth communications module.
You can pop together simple robots with motorized wheels that react to sound or light in seconds and, when you get bored, tear them apart and build something new. The kit is available for pre-order now for $150 or $400 for the Advanced Builder Kit, which comes with far more bits.
I am actually pretty excited for this. Don't be surprised if you happen to see a review I make on this product in the near future!