Rocket Fuel (Future Service)
This could be a very large market. Earth's "gravity well" requires a lot of fuel to launch any rocket into space. The ability for a rocket launch company to use a low earth orbit supply of rocket fuel will greatly increase the company's payload capacity as the fuel will be available for them in low earth orbit rather than their having to also launch extra fuel from earth.
This service could also provide for safer launches as rockets would not have to carry the large volumes of fuel that are currently required.