Obama is NOT in any way a libertarian. However, the goals of libertarianism (well, at least cosmorangelinebeltwaytarianism), and - for that matter, Burkean conservatism, are fundamentally liberal in the classical sense: a meritocracy in which economic and social mobility are maximized. The major difference between the Progressive, libertarian, and Burkean conservative are the means in which these goals are to be accomplished.
Again, I could not disagree more with Obama on many of his policies. Yet I find myself drawn to supporting him - passionately, even - because his goals are liberal in the classical sense. I repeat - I do not think his means are libertarian in any way, and are arguably not even classically liberal means. But the goals, so far as I can see, ARE classically liberal. His are not goals centered entirely around maximizing his own political power, and thus he is a candidate worthy of my deep respect. These ultimate ends are the same ends as exist for us perjoratively-named cosmo-libertarians (as well as for other derivations of classical liberalism).
***UPDATE*** From Caroline Kennedy's endorsement of Obama (to appear in the Sunday NYT):
I want a president who understands that his responsibility is to articulate a vision and encourage others to achieve it; who holds himself, and those around him, to the highest ethical standards; who appeals to the hopes of those who still believe in the American Dream, and those around the world who still believe in the American ideal; and who can lift our spirits, and make us believe again that our country needs every one of us to get involved. (emphasis added).
This paragraph of Kennedy's beautiful if unspecific endorsement best sums up why I'm able to support Obama. Much of Obama's appeal to me is in his apparent desire to encourage rather than require moral behavior. If government is necessary, a libertarian should be much happier with a government that relies on encouragement more than mandates. Though this is nothing compared to a lack of any government or a government confined to truly libertarian principles, it is still a vast improvement over most politicians' views of government.
More at memeorandum.