NASA is currently undergoing a crisis of strategy due to its lack of a specifically stated longterm goal. While its short-term mission statements keep changing, as do the various details of which rocket is to be used for what mission, its unstated but strongly implied goal of human colonization drifts further and further out of reach.
During his 2011 keynote ISDC address, XCOR's Jeff Greason set forth the backbone of a combined public/private strategy with the ultimate goal of longterm human settlement throughout the inner Solar System. The 42 minute video seen here on Youtube shows the majority of Greason's speech giving details about how settlement can potentially be achieved using only NASA's current and foreseeable budget and the cooperative profitable activity of private space corporations.
The main points of the speech are to have an overarching goal to set before congress, to develop and use In-Situ Resource Utilization for sources of propellant (which is to be sold by private corporations to NASA and to other interested parties), to focus NASA's priorities on researching technologies that cannot easily be developed by private industries (such as research on the effects of cosmic radiation outside the magnetosphere), and to build in clearly defined "planet-hopping" steps towards the explicit goal of human colonization of space.