So everyone is getting ready for Jackson and Del Torro's big "Unexpected Party" chat on Saturday, and we're seeing more stuff like this neat "Seven Things We Want From 'The Hobbit'" post. But I think there's some real confusion about what's being done with the two movies that will make up "The Hobbit".
Most people seem to be of the impression that we'll get the entire The Hobbit novel in movie one, and then some sort of bridge story to LotR in the second movie. I could be wrong, but that's not the way I understand it. Instead, what I've been led to expect is a weaving of The Hobbit with what Gandalf is up to every time he leaves, as revealed in Appendix material from the LotR books and Tolkien's notes. In terms of The Hobbit, I expect the break between the two movies will happen either right after Bilbo and the dwarves run into the wood elves, or right after they leave the wood elves. Meaning we won't get much Smaug or the Battle of Five Armies until the second movie.
So what was Gandalf up to every time he left the dwarves and Bilbo (usually just before disaster of one sort or another struck)? He was checking out a mysterious wizard lurking in the southern parts of Mirkwood who went by the ominous title "the Necromancer". These investigations tie in directly to the events of LotR, and will, I assume, be the promised "bridge" between the two groups of movies.