Sometimes it’s the simple things. Recently my wife and the geeklet went looking for a gift for his friend’s third birthday. They happily chose… a bag of rocks.
Polished stones, actually, chosen from one of those "Learn All About Minerals!!!" bins and accompanied by their own velvet bag and explanatory pamphlet. Well, it turns out that among the Barbies and ponies she got that day, this little bag of rocks was the instant favorite. That night she made mama read her that whole pamphlet and identify each rock, repeating the names for herself. She now carries that bag of rocks with her everywhere.