Phil Plait has an interesting discussion of what our future on the moon looks like. I've always been more interested in Mars myself, because it seems to offer more potential for the first non-Earth human civilization, but the Moon is almost surely going to play a role in our early interplanetary ventures. The idea that Phil outlines involves the Moon as a stepping stone to asteroid mining.
The key here, from an economics perspective, is to note that these are very long-term investments and even if they have shorter horizon payoffs the bulk of their benefits are going to accrue to future generations that can't demand these services now. This is the problem of what I call "temporal autarky" that I used to talk about on here every once in a while. Normal "autarky" makes us all poorer because we're not trading with other (contemporary) humans. Temporal autarky makes us poorer because we don't have the opportunity to trade with future humans (say, the residents of New America on Mars in 2512). Autarky limits particular trade flows depending on the economies in question, and temporal autarky is no different. Specifically, it limits trade in what we can produce that the future would want - for example, pioneer bases and infrastructure on the moon and Mars.
What that means is that insofar as market forces drive our interplanetary settlement, they're going to be restricted to settlement patterns that incentivize contemporary humans trading with contemporary humans, which means relatively short-horizon returns on investment (and even those will be long horizons relative to most other investment opportunities).
Of course we humans don't just do things through markets. There is also a role for public investment here and for non-pecuniary motivations.