Pikey

I would say put a station in Laythe orbit, as it will be the moon most visited (within the Jool system) and any mining operations on other moons would probably be fuelling something on Laythe. It is also very easy to get to after an aero brake from Jool, and it looks really nice when you get Jool rising over the seas of Laythe as you refuel.

Voted KSP - beats all the others easily and is not even finished yet *first post*