This is purely hypothetical as I don't have any child on the way (for the time being), but I've always fancied giving my (imaginary) daughter a middle name that is from a children's book. I loved reading as a child, and always thought it would nice to be able to share a name with a really good character. So thinking about it I've come up with:
Matilda and Sophie (Roald Dahl)
Lucy (Narnia)
Georgina (Famous Five)
Hermione (yes way too obvious!)
Charlotte (ok is a spider but still)
Heidi
Lila (couple of Philip Pullman books)
There must be plenty of others, any suggestions?