http://magnatiles.com/

These tactile, colorful translucent Magna-Tiles® are sized just right and easy to use, whether creating designs on a flat surface or building in 3-D. Basic shapes are learned through play. Magna-Tiles® develops patterning, shape recognition, building and motor skills. Use them for guided activities or hours of open-ended fun and exploration. They will work well alone or together with the solid colored Magna-Tiles ® to make windows, skylights, etc. Perfect for classrooms and multi-child play.