I prefer to steal from books (especially older ones), since it is less likely my players have read the book than seen the movie. If I include a movie reference it's usually as a joke.
I have stolen ideas from these books:
The Mysterious Island (Verne)
The Adventures of Doctor Dolittle (Lofting)
Treasure Island (Stevenson) (surprisingly none of my players had read this and had only seen the Muppet version)
Various Conan stories (Howard)
Dunwich Horror, Mountains of Madness (Lovecraft)
Sir Gawain and the Green Knight (original author unknown)