The Sun, the Moon and Gender

Here's something I've found interesting. In all the romance languages, the sun is masculine (el sol in Spanish, etc.) and the moon is feminine (la luna, etc.). But in German, it's reversed: the sun is feminine (Die Sonne) and the moon is masculine (Der Mond). Presumably this comes from differing mythologies that have given rise to these words. So my question to the group is a) what is the basis for this difference, and b) what is the gender for sun and moon in other languages? Any other nouns that work like this?

ETA: Thanks to everyone for your interesting answers ;)