Space has a lot of potential as a source of natural resources and energy. I think I reproduced in a post a paper I wrote some years back on asteroid resources, but I can't locate the post now. I may repost it at some point.

Suffice it to say that there are a lot of resources out there that you can get at without having to deal with a gravity well, even one as small as the Moon's. And a LOT of solar energy.

Jerry Pournelle has pointed out that for the billions we have spent over the past decades pacifying the Middle East and sucking up to nations like Saudi Arabia, we could have built a network of solar power satellites, and told the oil shieks to go jump.

The kicker is to find an application for space flight that is near term, yet profitable enough to bootstrap into the heavier applications like power satellites and asteroid resources. I personally think tourism has potential here. I had been hoping back in the Skylab, early Shuttle and Mir days that someone would find a highly profitable product that could only be manufactured in space, but nothing along those lines has shown up yet.