The US Department of Defense has announced the release of the 2008 National Defense Strategy (NDS) (29 page pdf). It's an interesting read. The document outlines the national approach to the defense of the United States and its interests. It starts by defining 5 major objectives of the DoD: defend the Homeland; win the Long War; promote security; deter conflict; and win our nation's wars. The document goes on to discuss how the DoD plans to achieve all these objectives "by shaping the choices of key states, preventing adversaries from acquiring or using WMD, strengthening and expanding alliances and partnerships, securing U.S. strategic access and retaining freedom of action, and integrating and unifying our efforts."
The NDS is issued periodically; the last one was published in March 2005.