It sounds like an oxymoron, but the concept of working in retirement is fast becoming the norm for many older Americans — forced by dwindling financial resources and a recessionary economy to stay in or return to the job market.

 Longer lifespans and a desire to remain productive and connected already had begun pushing the number of older workers higher. Now the financial crisis is accelerating interest in working later, with career sites and organizations for seniors and older workers reporting a surge in job-hunting efforts.

 Sixty-three-year-old Marian Austin of Alfred, Maine, is among those who need to work again just to make ends meet in retirement. In this economy, her late ex-husband's Social Security isn't nearly enough.

 "It's been difficult," said the former gift shop owner and retail manager, who retired two years ago. "I don't know how I will pay for fuel oil for heating. I can't walk into a grocery store and buy what I want. I don't look forward to Christmas because I can't buy gifts this year."

 AARP, the nation's largest advocacy group for older Americans, saw dramatic evidence of the trend in September when more than 2,000 people attended its annual job fair in Washington, D.C., more than double the previous year's attendance. The job-seekers included many who had been recently laid off and retirees worried about the economy and the pressure on their limited resources.

 "We've definitely seen an increase in the sense of urgency in terms of jobs," said Deborah Russell, the organization's director of work force issues.

 A market for retirement jobs essentially emerged a decade or so ago. Now postings for those at or approaching retirement age are an important and growing phenomenon in the labor market, as evidenced by online job boards that include RetirementJobs.com, RetireeWorkforce.com and Seniors4Hire.org, which cater to not just retirees but anyone 50 and older.

 Demand for such resources is only likely to grow with the graying of the work force expected to continue. Workers age 65 and over are expected to account for 6.1 percent of the labor force by 2016, up sharply from 3.6 percent in 2006, according to the U.S. Bureau of Labor Statistics.

 "For decades we've been making it easier for people to get out of the labor market," said Marc Freedman, CEO of Civic Ventures, which focuses on helping older baby boomers launch second careers involving social contribution. "Now there's a growing need in the opposite direction."

 Despite the increased opportunities, seniors may find the job market for them is as tight as for everyone else in a struggling economy.

 Going back to work part-time should help Austin get by, but getting hired for a worthwhile job in retail, merchandising or working with disabled people is proving tough. She wonders if age discrimination is a factor.

 "A lot of these folks who are hiring are in their 20s or 30s and they think people in their 60s are ancient," she said. "If it comes down between you, with a lot of experience, and a younger person, I feel they're going to go with the younger person."

 One concern is that, despite their strengths, older workers often are perceived to resist training, dislike answering to younger bosses or have poor computer training, according to AARP's Russell. Seniors need to assess their skills and seek out job-searching tips, particularly if they haven't gone through the process in recent years, she said.

 "The job market has changed," Russell said. "Employers are accepting job applications online, they expect to see your resume online, interviewing has changed, so it's important to keep up."

AARP has a program that helps age 50-plus workers with job opportunities — its National Employer Team, which connects job-seekers with a wide variety of opportunities.

 RetirementJobs, which lists more than 30,000 jobs across all 50 states, has seen a surge of retirees come to its site since the economy soured, with traffic doubling to 400,000 visitors a month between July and September.

"About four to six months ago we started seeing a significant new group of people, already retired, who needed to return to work," said Bob Skladany, chief career counselor at RetirementJobs and an adviser to AARP on work-related issues.

On top of that, he said, the wave of layoffs this fall has been bringing in younger job-seekers from 50 to 53.

 The good news is there are still plenty of jobs available for the 50-and-up work force, he said. Sectors that are hiring in significant numbers include health care and home health care, retail and hospitality, and customer service openings of all kinds exist, Skladany said.

On the plus side, mature workers appeal to many employers because they are seen as hard-working and more dependable and loyal than younger peers. That makes it much more common for companies to now hire people up to their mid-60s, according to Bob Hoberman, a partner at Holmdel, N.J.-based RW Consulting Group, which operates RetireeWorkforce.com.

Still, getting hired at 65 or over by a new firm can be challenging, he said. Employers may not want to hire older workers because of health concerns or other issues.

 "I think companies certainly are looking to retain their own people over 65, and it's not going to be unusual at all for people to work till age 70," Hoberman said. "But whether they're as willing to hire someone over 65 from the outside remains to be determined."

 50-and-over population. Also includes targeted career resources and articles for older workers.

 • WiserWorker.com (www.wiserworker.com) enables baby boomers and older workers to search for job listings by keyword or location and provides career articles and resources plus listings of local job fairs across the country.

 • YourEncore (www.yourencore.com) seeks to match retired engineers and scientists with companies that need to meet a capacity surge or fill a short-term need, with clients that include Fortune 500 firms such as Boeing, Eli Lilly and Procter & Gamble. The retirees sometimes are brought in as temporary mentors for new hires.