Why such an interest in — and growing acceptance of — portfolio careers now? For one thing, corporate job stability has all but disappeared. In addition, the workplace is changing from the perspective of both employee and employer, Challenger says. "Companies are increasingly hiring specialists in specific areas who can come in and consult or do project work," he says. Technology also allows for a more mobile work force, making it easier for a would-be portfolio careerist to be reachable when not on the job. And survey after survey indicates that people are looking for not just more work-life balance but also more satisfaction from their work.

On the other side, "employers are waking up to the notion that flexibility makes economic sense for them, too," says Alboher. Moving in and out of corporate America also carries much less of a stigma than it did in the past, largely because "organizations are looking for the best talent and the best experience for the job regardless of whether that person has had a traditional one-track career," says Kim Bishop, managing director of Korn/Ferry International, an executive recruiting firm.

That is certainly the perspective of Lynn O'Connor Vos, president and chief executive of Grey Healthcare Group and one of Gold's bosses. She sees having the insight of a practicing doctor on staff as a great advantage for her team. "He gives us a reality basis we wouldn't have," she says, "and it doesn't matter whether he is here every day or not."

The more successful portfolio careerists tend to establish themselves in a specific field and then cut back to make room for something new. Litigation consultant and cartoonist Karl Hampe spent nine years working 80 hours a week at BDO Seidman, a national accounting and consulting firm.

But two years ago, Hampe, 44, decided he wanted time to pursue one of his passions, cartooning, as a second career. He wrote a proposal for his employers at BDO Seidman that outlined a 25 percent pay cut for a three-day-a-week schedule (he stayed on three days to be eligible for health-care benefits). His employer agreed to the plan. "When I need to work more than that, I do," says Hampe. "But the key is that I have more flexibility." The other two days a week, plus weekends, Hampe works on his weekly comic strip, The Regulars, which he introduced last year on the Web. Recently, the New York Blade picked up his comic strip in print.

For others, like Rita Foley, leveraging corporate experience into a multipronged path works best. Foley spent 33 years in the corporate world, ending her career as global president of MeadWestvaco's $1.1 billion consumer-packaging group. She now divides her time equally among working as a career coach for C-level executives, a corporate director at PetSmart and Dresser-Rand, and a nonprofit board chairman at Pro Mujer (a women's microfinance and health organization). In her spare time she is writing a book on sabbaticals.

Despite the benefits of workplace flexibility and increased job satisfaction, pursing a portfolio career can have drawbacks, including stalled earning power and trouble maintaining company-sponsored health insurance. Dan Milstein knows this all too well. The 37-year-old earns his living as a partner and computer programmer for a Boston-based start-up, working 20-plus hours a week from home. And 10 years ago he founded Rough & Tumble Theater Co. He writes, directs and produces two plays a year but says he doesn't earn as much money from these pursuits combined as he could, say, focusing on the programming career alone.

Neither gig offers health insurance, so Milstein has been footing the bill for his own medical coverage for the past decade. But, he says, it's a worthwhile expense because "I don't think I could be entirely happy doing one thing."

Being able to wear two or three hats and change them up day by day can be a challenge, too. Both Gold and Hampe say there is a period of "re-entry and readjustment" each time they walk into one office after spending time at the other. "I am constantly triaging and deciding what project needs attention most," says Gold, who often jokes that he has two three-quarter-time jobs.

To make a portfolio career work, "you don't have to be great at multitasking," Alboher says, but you must "be incredibly focused."