Read it in context. Preferably the whole book. At this point, Paul has said that when God told us what he wanted from us (by means of the Old Testament Law), mankind as a whole rejected it and did our own thing. Paul's basically addressing exactly what the other poster said - if God can forgive our sin, why don't we just sin more so God can forgive more? He answers that by saying that when God forgives our sin, we are supposed to be different in the future. It would be wrong to take advantage of it. If this doesn't help, hit me on XMPP at email@example.com and I can try again.
I haven't read it cover to cover, but I've read more than enough of it over the years to know that aside from some common sense stuff and good old folksy wisdom, much of which predates the Bible anyway, most of the rest of it is just very boring or very crazy. That these things have been reinterpreted (read: spun) so much over the years that people get less of the crazy in sermons is probably a good thing. I'm not entirely convinced of that though, as it also allows them to have misunderstandings about their religion. Then again, religion is rather meaningless in the overall scheme of things, as it is only actions that matter. Most Christians haven't read the Bible cover to cover anyway. If they could make any sense of it, they'd probably be rather shocked by some of what they find.
There are about as many interpretations of the scripture as there are believers. People generally believe what they want. Of course these days it seems that these fringe groups are growing larger and embracing the crazy wholeheartedly. Look at Perry or Bachmann and the crazy stuff that they believe. Look at who was leading Perry's prayer event. These guys are truly nuts, and they're running for the most powerful position in the world.