The Blizzard by Betty Ren Wright

A  boy's birthday party is cancelled due to the possibility of a storm blocking the roads.  During school a blizzard starts in full force, and the many of the children are stranded.  The birthday boy's house is the closest one.  He winds up getting his birthday wish in an unexpected way.

How High is the Sky by Anna Milbourne

Pipkin the penguin wants to know how high the sky is.  He has a bird and a hot air balloon take him up, but can't find the end of the sky.  Fold-out poster illustrates how high various parts in the sky are, all the way up to the moon, but the sky is still bigger.

How Big is a Million by Anna Milbourne

Pipkin the penguin wants to know how much a million is.  So, he searches to find things that are big.  He finds, 1, 10, 100, 1000 and more, but he has trouble finding a million.  Finally, in a fold-out poster at the end, his mother shows him a million of something.  Great for illustrating how huge a million really is.