First Men in the Moon is a 1964 science fiction film based on H.G. Wells' book with the same title. Nigel Kneale (Quatermass II, Quatermass and the Pit, Nineteen Eighty-Four) wrote the screenplay. Ray Harryhausen (Beast from 20,000 Fathoms, One Million Years B.C., Earth vs. the Flying Saucers, It Came from Beneath the Sea, 20 Million Miles to Earth) did the special effects.
The Younger Son and I had an interesting little discussion on whether or not this movie is Steampunk.
Youtube has it online in 10 sections. Part 1:
part 2, part 3, part 4, part 5, part 6, part 7, part 8, part 9, part 10
Moria has a review. TCM has an overview.
5/30/2010: FilmFanatic has a review.