30 entities or works in the U.S. public domain. I find these to be creatively inspirational, and judging by the number of adaptations, others seem to think so as well.
Some quick notes:
It's specifically the first 26 books of the Oz series that are in the public domain.
The Anne Authority does not condone images of words, characters, places, & events in the bks for the available AoGG books.
Peter Pan the play remains under copyright for Great Ormond Street Hospital.
Hope you enjoy these!