From NBC's Mark Murray
According to senior Obama aides, who briefed reporters on Obama's speech before he delivered it, the initial meeting to begin drafting Obama's inaugural address took place before Thanksgiving, when Obama first laid out his thoughts. Obama, they said, wanted to discuss the moment that America finds itself in right now, and believed some of the best inaugurals -- Lincoln's second and JFK's -- did just that.
After that first meeting, the speechwriters began working on a first draft; they then worked on other drafts. And the weekend of Jan. 9-11, working from the Hay-Adams hotel in DC, Obama did some extensive editing and wrote the bulk of the final draft.
When asked about the division of labor between Obama and his speechwriters, one of the aides answered, "What you'll hear ... is from [Obama]. It is, in many ways, his own speech."
Obama's speechwriters also consulted with some outside advisers, however: JFK speechwriter Ted Sorenson, historian Doris Kearns Goodwin, and historian David McCullough. They all saw a fairly final cut of the speech.