Comment Magna-Tiles (Score 1) 458
I would recommend Magna-Tiles, which my 4 and 2-year-old daughter love.
http://www.amazon.com/Magna-Tiles-Translucent-Colors-100-pieces/dp/B000CBSNRY/ref=sr_1_1?ie=UTF8&qid=1290294910&sr=8-1
A successful [software] tool is one that was used to do something undreamed of by its author. -- S. C. Johnson