I mainly wanted to call your attention to this website: The SIBL Project, an organization that promotes adult literacy by using "music as a vehicle to engage, inspire and reinforce the magic of literature and the power of reading."

Their list of famous SIBLs is fun to browse (though it's discouraging that it contains so many typos).

They also sponsor a yearly songwriting competition.

What songs inspired by literature are you aware of? If they're not already in The SIBL Project's list, I'll collect them and e-mail them to The SIBL Project.