With all the talk of space elevators, I had to bring up what I think is a better approach. The space pulley is basically two elevators, one going up while one goes down. When you need to launch something into orbit, you put your satellite on the elevator at the bottom, and someone up at the space station puts something even heavier on the elevator at the top. Gravity pulls the heavy object down and the pulley lifts your object up. We use friction to keep the speeds reasonable.
What would we want to bring down?
The first thing is space junk. There's lots of it up there, and you can sell it on eBay.
The second thing, once you've exhausted space junk, is asteroids. With these, you can lift up really heavy satellites (which will become the space junk of the future), and you can bring down some raw materials which will be worth plenty in the commodities markets.
The third thing, which might be harder to find, is comets. You can bring some comets down in Egypt to provide fresh water to irrigate the rest of the country.
You might also want to bring things down to harness the gravitational energy. As with hydroelectric dams, you can generate energy when things fall.
Don't tell me it's impractical. The description of my blog is Amit has crazy thoughts, so I'm required to post things like this!