MIT grad student David Merrill and his team created a set of computerized toy blocks, called Siftables, that are aware of each other. Because the blocks are aware of their own orientation and (to some extent) surroundings, they can interact with each other. For example, around 2:30, Merrill shows a demo of addition via blocks -- by moving around blocks labeled "2" and "3" as well as "+" and "=", the blocks can sum themselves, forming a sort of interactive math problem.
Merrill's Siftables demo is only seven minutes long, but it shows great promise -- for learning, play, music, photo display, and many other applications. When these blocks become commercially available, you can bet they'll be the newest must-have toy. Check it out: