Over in the FR thread, Fogbowers discussed the difference between U3 and U6 measures of employment, underemployment, and unemployment. The John Birch Society house organ, "Human Events," offers its own measure:
What is the current percentage of working-age Americans, eligible to participate in the civilian labor force, but not currently working? Answer: 36.3 percent.
That’s the worst labor participation rate in three decades, and it’s part of the worst employment picture we’ve seen since the Great Depression. Labor force participation is the number we should really be looking at, even more than the unemployment figures cooked up on the monthly basis by the Bureau of Labor Statistics. Those figures have their uses as well, but it seems reasonable to measure the overall health of the economy by the number of people who simply are not participating in the labor force.
This would always be a much higher number than the BLS unemployment statistic, even when the economy was humming along at maximum power. There are always going to be working-age people who drop out of the labor force, for reasons that have nothing to do with the nation’s overall economic health. The labor force participation rate hasn’t exceeded 67 percent in the past decade, so we would be looking at a true “unemployment” number that bounces between roughly thirty and forty percent. The difference between good and bad percentages is relatively small, which makes the true “unemployment” figure less sexy for news coverage, and therefore less useful to politicians… but it’s more logical to measure small changes in a large, accurate number than big changes in a small, largely fantastic number.
Writing at Red State, Rep. Jim Jordan (R-OH), who chairs the House Subcommittee on Regulatory Affairs, Stimulus Oversight, and Government Spending, offers an eye-popping chart measuring the effect of President Obama’s “stimulus” policies on workforce participation:

Notice that the Y-axis has been constrained so as to show the maximum impact. Also, note that the X-axis is similarly constrained to the last decade. There is no historical context here.