What economist Dean Baker said:

We know how to get out of this mess, we have known how for 70 years. We just need the government to generate demand. That means spending money. Ideally it would spend money on useful things like education, health care, and infrastructure, but even if it spent money in wasteful ways it would still create jobs and put people to work.

In the 30s we got much of the way back to full employment with the Works Progress Administration and other programs. Much of what was done was useful — look around, you won't have to go far to find infrastructure built by depression era programs. However, it took the massive spending associated with World War II to get the economy back to full employment. There is no magic associated with war that makes military spending more effective in creating jobs. The only difference was the that the threat to the nation from the Axis powers removed the political obstacles to the necessary spending.

One of the knee-jerk right-wing rejoinders to demands for a Keynesian response to our current economic crisis, is that it was World War II, not FDR's New Deal that ultimately pulled us out of the Great Depression. But as Baker points out, that's not a refutation of Keynes. Massive government spending is massive government spending, regardless of what you spend it on.

All we're lacking is the political will.