The Beeman, written by Laurie Krebs and impeccably illustrated by Valeria Cis, is a cute and very educational book about a little boy whose grandfather is known around town as "the beeman". This is, of course, because his grandfather is a bee keeper. In my opinion, children as young as 3 will enjoy this book, although the official recommendation is ages 5-9.
"Barefoot Books World Atlas", written by Nick Crane and illustrated by David Dean, is a wonderful tool for learning. There is a very large pull-out world map in the back, sections on each geographic area, and lots of interesting tidbits for young--and not-so-young--students.
The "Words Books" are three largely identical books: My Big Barefoot Book of Wonderful Words, My Big Barefoot Book of French and English Words, and My Big Barefoot Book of Spanish and English Words. Wonderful Words has the words in English only, and the other two have them in English and French or Spanish.
The Barefoot Book of Children is, quite simply, the most powerful children's book I have ever read. (And yes, that includes To Kill a Mockingbird and The Little Prince, my two previous favorites.) And all of my children (including Atticus, when he was alive) are just fascinated by it.