Introduction: a different kind of college ranking.

It wasn't long ago that the colleges annually anointed as "America's Best" by U.S. News & World Report--Harvard, Princeton, and Yale--served as fertile breeding grounds for future masters of the financial universe. History majors from New Haven could make the hour-long drive along the Long Island Sound to the hedge funds of Greenwich, Connecticut. The Harvard-to-Wall-Street pipeline was open full bore.

Then all those smart people destroyed their own companies and almost brought the global economy down with them. The credit markets collapsed, demand for goods and services plummeted, and millions of innocent workers lost their jobs. Today's college graduates face the worst labor market in generations.

As a result, many are looking to do good if they can't do well. Applications to the Peace Corps jumped 18 percent in 2009. The number of students vying for Teach for America slots increased from 18,000 in 2007 to 46,000 this year.

The renewal of a desire to serve is heartening. But the truth is that while jobs that allow you to lose billions of other people's dollars and wreck the economy before you turn thirty have traditionally been limited to graduates of a few select institutions, a steady focus on service has not. Many colleges that fall in the middle of the U.S. News pack (or lower) have long been more inclined to spend energy and resources on encouraging students to give back to their communities and their nation, and not just themselves.

Calling attention to these service-oriented schools is one of the reasons this magazine got into the college-ranking business in the first place. When we published our first ranking in 2005 (with the expectation that it would prove a point rather than become a tradition), the idea was to upend the traditional notion of a college guide. Instead of asking what a college could do for you, we asked, "What are colleges doing for the country?" Yes, Yale might educate a disproportionate number of future hedge fund managers. But is it laying the foundation for the kind of nation we want to become?

After all, colleges and universities do as much to shape the future as any institutions you can think of. They conduct cutting-edge research that drives economic growth, provide upward mobility to people of humble birth, and mold the characters of tomorrow's leaders. And they are supported in these endeavors with hundreds of billions of dollars in government subsidies. So we all have a stake in knowing how well schools fulfill their public missions.

But while there are plenty of guides out there that help students and parents decide how to spend their tuition dollars wisely, there wasn't one to tell citizens and policymakers which colleges were spending their tax dollars wisely. So we devised a way to measure and quantify how well individual colleges and universities were meeting their public obligations in the areas of research, service, and social mobility (see "A Note on Methodology," page 86), and we ranked schools based on the results.

The full rankings for national universities and liberal arts colleges begin on page 62. This year, we've also provided a top fifty ranking for three other categories of schools: master's universities (page 58), baccalaureate colleges (page 60), and community colleges (page 48). And in...