In addition to selenology (which is a big deal because no celestial bodies other than Earth are so far extensively explored) and places for telescopes, Moon can be a source of some metals (Al, Ti, Fe), oxygen and some other elements, perhaps hydrogen. By mass metals and LOX/LH2 could be the majority of mass transported in Moon-Earth space in near future. Other important payloads are electronics - relatively light - and humans.

So Moon can supply vast majority of material needed for operations in Moon-Earth space. You can maybe launch the materials using a mass driver (some demos here - http://ssi.org/mass-driver-demonstration-tapes/), but even more conventional technology will give you results.