There was a time when a business leader was someone straight from Central Casting. They were the suit-clad CEOs of the alphabet-soup companies--GM, GE, IBM, AT&T--at the pinnacle of American business. Times change. The men and (occasionally, at least) women who now lead the biggest U.S. corporations still matter, and size still matters as well: business will always be a game in which the score is kept in dollars.

But ideas matter, too. So in this installment of NEWSWEEK's series on 21st-Century Leadership, we're highlighting men and women whose influence isn't measured by old-fashioned indicators like the number of employees they manage or the board seats they hold. Instead, these New Thinkers are leading industries in whole new directions. In the profiles that follow you'll meet an executive who's convincing customers who love $4 cups of Starbucks coffee that they should also turn to the chain to buy music. Another is proving that nowadays some of the best advertisements won't appear on television during the Super Bowl--they'll air on your computer screen. The most famous of these New Thinkers have already created iconic New Economy businesses--eBay and AOL--and now they've begun innovative second acts.

If you suspect their jobs are more fun than those of traditional big-company bosses, you're probably correct. This has been a tough year for leaders of all stripes, especially recently dethroned CEOs like HP's Carly Fiorina or Merck's Raymond Gilmartin. In the United States, 441 chief executives left their jobs during the first four months, according to Challenger, Gray & Christmas, a pace that's 88 percent ahead of last year. The rising rate of executive turnover has led to talk of a "leadership crisis" as boards struggle to fill what were once considered plum jobs. Doesn't anybody want to be CEO of Boeing?

These New Thinkers are part of the first generation raised in an era in which leadership has been taught as an academic discipline. From executive coaches to M.B.A. courses to acres of shelves in libraries, there's nearly as much advice today on how to improve your leadership skills as your sex life. But all this advice raises a question: has the burgeoning be-a-better-boss industry actually produced... better leaders?

The answer is yes, to a degree. First, the increased attention on bosses' people skills has led to less tolerance (by boards, shareholders and employees) for bad leadership than in the past. Second, managers are proving more able to jump between industries today, says recruiter Gerard Roche of Heidrick & Struggles, who's brought industry outsiders in as CEOs at Home Depot and 3M in recent years. Another factor: while in the past aspiring leaders mostly tried to emulate good managers, today there's newfound interest in learning from managerial train wrecks, like Howell Raines at The New York Times. And as power has flowed downward in organizations--driven not just by benevolent bosses, but also by technology like blogs that make organizations more transparent--the pressure on leaders to act appropriately will only grow. "This will keep leaders more in line in the future--we're simply watching them too closely now," says Barbara Kellerman, a Harvard professor and author of "Bad Leadership: What It Is, How It Happens, Why It Matters."

Among younger workers, there's also more recognition that leadership isn't simply a function of job title. When Warren Bennis, an 80-year-old professor who's been exploring leadership with students at MIT, Harvard and USC since the 1950s, asks today's young people to name the leaders they admire, they list people like Steve Jobs, Oprah Winfrey and the founders of Google--rarely does a Fortune 500 boss show up (and politicians are even rarer). People in their 20s and 30s were raised in a time of wider options, he writes in "Geeks & Geezers," a study of generational leadership styles. Many realize that today the best way to become a leader isn't to spend 20 years slogging upward at a corporate behemoth--it's to strike out and start your own gig, which you'll lead from day one.

You can make an argument that society's focus on leadership is over-blown: in truth, no matter how ambitious we are, most of us spend more of our lives as followers than leaders. But as business gets more complicated and workdays grow ever longer, bosses will have little choice but to delegate more and micromanage less. In today's world, like it or not, you may be a leader sooner than you expect.