I find the "moony 11" rule to be fairly reliable--the full moon is f:11 at 1/ISO.

This is, of course, much brighter than the moonlit landscape, so the thing to do for landscapes with the moon is to try to mask out the moon using a matte box in front of the lens, photograph the landscape without the moon, remove the mask, and then add in the moon at f:11 at 1/ISO, which will have virtually no effect on the rest of the exposure.