In the neverending quest to find great products to fidget with, PixelBlocks has recently become the collective favorite here at the ThinkGeek conference room. They are tiny, translucent blocks/cubes that come in a dozen different colors. Simply connect them (either horizontally or vertically) and you can instantly build visually stunning creations in either 2-D or 3-D. The number of colors available to you means you can even create photo-realistic designs, commonly referred to as 'digital stained glass' (DSG) in the PixelBlock community.
PixelBlocks
