"I'm 40 years old, and I've worked in corporate America since I was 21," says Lisa Ellerton, who had climbed her way up through the insurance business until she was the worldwide operations leader for Royal & SunAlliance. One day, Ellerton asked her sister and her sister's friends why they didn't ever take time for themselves to go to the gym. The Orange County, California, denizens were all looking for something that was convenient but that didn't make them feel guilty for leaving their kids for the StairMaster.

And just like that, Ms. "Super Corporate America" began to drop out. Ellerton left Manhattan for Manhattan Beach, trading in her power suits for PowerBars. She began planning a fitness studio, catering to executives in the morning and evenings and to stay-at-home parents and their kids in between.

In doing so, she joined the ranks of those who ditched the corporate life in favor of their own startup. Dropping out connotes '60s-ish notions of Timothy Leary and Easy Rider, but it's not quite that simple and doesn't come in convenient pill form. Making the transition from glass buildings, 401(k)s, and dental plans to a much more unpredictable but potentially more rewarding life involves planning, finesse, and a little luck. By the time Ellerton's first studio opens this summer, it will have been nearly three years since she envisioned it, most of that time spent working for the Man.

Tune in to ideas around you

Breaking out of the corporate grind starts with an idea, and the good news is that ideas abound in the work environment. Jason Finger and Paul Appelbaum's company started with a growling stomach. The two law-school buddies were regularly toiling away in their respective first-year associates' jobs and debating the merits of chicken lo mein versus pepperoni pizza when comparing the takeout options near their midtown Manhattan offices. Looking at the jumble of menus in their desks, and the hassle of remembering which client to bill, the two stumbled on the idea that would become SeamlessWeb Professional Solutions, an online food-delivery service for law firms, bankers, and so forth.

"We understood who the clients were, we understood who the users were," Finger says. During the cold January when he and Appelbaum were completing their plans, he couldn't help but smile every time an associate complained about venturing outside in the cold and rain for lunch, "because I knew that we could help people out with a real problem."

It was confidence in this idea -- or chutzpah -- that led Finger, just five months into his first job out of law school and $100,000 in debt, to leave a career in law behind. "A lot of entrepreneurs actually get their ideas for their business while working at a company," says Herminia Ibarra, a professor of organizational behavior at INSEAD and author of Working Identity: Unconventional Strategies for Reinventing Your Career (Harvard Business School Press, 2003). "They see a need that's not met." Finger has long since paid off his student loans -- and SeamlessWeb's 2004 revenue hit $50 million.