One obvious example is manufacturing in zero g. parts can be thrown from operation to operation, rather than having to trundle along on a conveyor. launch would have to get pretty damn cheap to make assembling cars in space worthwile
A better example might be fancy chemicals. Rather than purchasing a "very expensive machine" to ensure a specific environment for reaction, it might be cheaper to send the materials to zero g for processing. I'm not a chemist, but watching astronauts play with bubbles and flames in space makes me think you could get a lot of precision by modeling everything as perfect spheres. So, the reactions are simper to model, easier to get accurate and precise outcomes.
It's wish fulfillment for sci-fi geeks, a deus ex machine made out of unobtanium which purports to answer the question "Is there any reason to go to space other than fulfilling the fantasies of sic-fi geeks given that getting to space is so fantastically expensive as to swamp all benefit of commercial activity other than artificial communications satellites?"
It's not quite that expensive -- NASA's budget from 1958 to 2011 was about $800 billion. To put it into perspective, the US has a yearly military budget of about $660 billion.
