There's more to retirement planning than padding your 401(k) and signing up for Medicare. Tired of endless hours of leisure and no set routine, some retirees return to their old jobs, find new employers or start their own businesses. Research by AARP has consistently found that about 80 percent of baby boomers say they plan to continue working, at least part-time, past the traditional retirement age of 65.

With the economy sound and the job market strong, many employers welcome the trend. Fearful of staff shortages after boomers retire, companies will offer experienced workers flexible hours, part-time schedules and innovative "snowbird" programs that let employees split a job between summer and winter locations.

Michael Jalbert, president of MRINetwork, one of the world's largest professional-staffing firms, says his company places an increasing number of retired baby boomers in jobs. "Companies seek people with the skills, experience and work ethic of that generation," says Jalbert. "It's a candidate-driven market."

Many employers also think older workers are just as productive as their younger counterparts, if not more so, according to a recent report by the Center for Retirement Research at Boston College. After surveying 400 employers, the center's staff concluded that managers and professionals have better prospects for extending their careers than rank-and-file workers. The report also notes that midsize employers (with 100 to 1,000 employees) offer the best opportunities for older workers.

On the downside, employers view older workers as more costly than their younger counterparts because of their higher salaries and benefits. So you may need to accept less money to land a new job.

Before you seek new employment, advises Jalbert, have a clear idea of how much you want to work, how far you're willing to commute and how much flexibility you need. You'll be miserable if you land in the same overextended, high-pressure situation that made you savor early retirement.

Other thoughts for boomerang retirees:

• Start with the company you're leaving. See if you can find a role as a consultant or as a trainer to help orient your replacement. Short-term assignments can morph into longer-term engagements.

• Look to the suppliers that your company uses. Assuming you have no conflicts of interest, your expertise and experience could be extremely useful to such an organization.

• Tap the network you've developed. Contact colleagues from professional organizations and tell them what you want to do. Keep an up-to-date resume.

• Consider other outlets. Many retired boomers are turning up as teachers, from elementary school through college (see www.teaching-jobs.org).