Iann Robinson posted a great list at the Crave Online site. With the enormous successes of the Harry Potter series and most recently, Where the Wild Things Are and Twilight, children's/YA books are as popular in Hollywood as Jane Austen books were in the 90s.
While I don't agree with all his choices (please, not The Giving Tree!), I think several suggestions, particularly Alexander and the Horrible, No Good, Very Bad Day and The Boxcar Children are terrific ideas. I think they are inspired choices; parents would definitely recognize them from their childhood, and they remain popular titles today.
If I were a Hollywood producer, I would green-light these titles:
A Drowned Maiden's Hair. Costume designers could go to town on the Victorian-era costumes. You have the supernatural element. The orphaned child and the sneaky maiden aunts.
Fly By Night. Humor, fantasy, and a crazy goose. Adventure. If you haven't read this, read it NOW. You'll understand.
Hello! Princesses! And a boarding school! More supernatural elements! A great title! Golden opportunity! You'll draw in little girls and their moms just on the title alone, people! Release it during the big Thanksgiving-Christmas movie season, and you're good to go.
Of course, the history of Hollywood is littered with lackluster, disappointing, and just plain awful adaptations of beloved children's books (exhibit A: The Cat in the Hat movie with Mike Myers). But paired with a great script and cast, these books could be wonderful movies.