A lot of things may not have held up or happened like he speculated (massive mechanical roads?) but I dare say that Robert A. Heinlein would be smiling today if he were alive to see one of the necessary features to one of his best novels, The Moon is A Harsh Mistress, has proven out. They've discovered water on the moon! Via Instapundit.
What an interesting and encouraging development. It appears a lot of water might be up there, buried deep under the surface. If there ever are hardrock "water miners" on the moon, I hope at least one is named "Manny".