You've decided to re-enter the workplace. How do you get your foot in the door to prove your worth? What kind of job can you expect to get? And what do you want to do — the same kind of work you did or something new?

The last question may be the first one that retirees must answer.

"What they need to do is find out where their passion is, what really punches their buttons and gets them really excited," says David Corbett, author of "Portfolio Life: The New Path to Work, Purpose and Passion After Fifty" (Jossey-Bass, $25).

Experienced job seekers can go to www.retirementJobs.com to search for and apply for thousands of full-time, part-time, seasonal and contract jobs, with employers representing a wide array of industries. To assure that jobs and the employers who offer them are suited to age 50-plus workers, RetirementJobs.com conducts an extensive evaluation of employers to verify that their policies and practices have proved successful in recruiting and retaining older personnel.

Companies that have been certified as "age friendly" include Borders Groups, REI, H&R Block and Oakwood Healthcare System.

"We make it easy for millions of older Americans to log on to discover work opportunities that fit both their income and lifestyle requirements," says Tim Driver, CEO of RetirementJobs.com.

Some senior-oriented job boards provide niche services. For example, YourEncore.com was created by Procter & Gamble and Eli Lilly to recruit scientists and engineers. The client list has since expanded. Another site, Alumni In Touch (www.alumniintouch.com), helps employees of big companies stay in contact with former colleagues.

That's how Ian Piesse found work when he retired at age 53, after a 28-year career in human resources with Shell Oil. Today, he works from home in a fishing village in Devon, England, interviewing candidates for other jobs at the oil company.

"I contacted a few of my ex-colleagues at Shell," he said in a posting on the Web site. "It was amazing how quickly it worked. Six weeks and I was back working again."

Many of the job-board sites and other retiree-oriented Web resources also provide tips for writing a resume and presenting yourself to businesses accustomed to hiring younger employees. One excellent resource for job-search guidance is AARP (go to www.aarp.org/money/careers and click on "Finding a Job").

To search for jobs with nonprofit groups, try www.philanthropy.com. For teaching positions, go to www.teaching-jobs.org. And if you're interested in starting a business, the U.S. Small Business Administration offers a start-up guide at www.sba.gov.