Mayra Alejandro

"Since the ninth grade I knew I wanted to work in the U.N.," says Mayra Alejandro, 40, a United Nations political affairs officer who helps schedule and organize the work of the General Assembly. "I knew I wanted to do something to help make this a better world, and to me, the U.N. was a place where things were done for the good of humanity." After 15 years, that sense of mission still sustains her. "Most people I know work to earn a living. When I wake up, I'm ready to go to work -- and I'm ready to stay there until I finish the job."

Fred Zuckerman

"Capitalism can be crude and painful," says Fred Zuckerman, "but it's also kind of wonderful how it can work. It's a lot of fun to buy a company and make it better." After many years as a corporate treasurer (for Chrysler, RJR Nabisco, and IBM), Zuckerman, 62, struck out on his own in 1995. A self-described merchant banker, he invests in everything from real estate to health care to garbage. "Every day there's a different transaction," he says. "Yesterday I was in the guts of Seventh Avenue, evaluating a clothing company. My experience in that area approaches zero. It was fascinating."

Laura Fernandez

When Laura Fernandez, 21, started working at the Save Mor Copy Center two years ago, she thought she'd be bored. But the job's turned out to be very satisfying. "Everyone gets along, everyone is calm, and we all laugh a lot." And Fernandez enjoys the interactions with the shop's regular customers: "It's like being a psychiatrist, or a bartender. They come in and tell us their problems."

She likes it so much that she's delayed plans to study accounting. "I know I can't work here for the rest of my life, but it's hard to imagine leaving."

Derek Roofayel

"I suppose it goes back to all the old movies -- you know, Gene Kelly, Fred Astaire, and all the old songs that make you want to move," says Derek Roofayel, 32, who has been in the competitive world of ballroom dancing in one form or another since he was 6. These days, as the owner of a Fred Astaire Dance School franchise, he teaches amateur competition students. "It feels great to help someone get to be as good as they can be," says Roofayel. "I'm making the circle larger. I'm giving back to the dance world what the dance world gave me."

Barbara Kairson

After two years fighting to get women into nontraditional fields, Barbara Kairson, 48, wanted a job where she could see she was making a difference. Now Kairson administers educational benefits for a municipal employees' union -- and gets that satisfaction. For example, she says, "we have a course for members with dyslexia. One student always wanted to be a chef. He came through the program, took the test for a culinary school, and was admitted." Says Kairson: "It reminds me that we can facilitate change. In a lot of jobs you never get to see that."

Kerri Mahoney

"I love the idea that you can have control of every aspect of what you do. You can change something like four times in 10 minutes. It pushes you to go further," says Kerri Mahoney, a freelance Web site designer. Schooled in filmmaking and animation, Mahoney, 26, jumped to Web design two years ago. She and boyfriend Peter Mack launched the award-winning kids' Web 'zine Jinx and are working on a site for Nickelodeon. "The coolest thing about doing what I do is getting e-mail," she says. At Jinx, one of her first letters was from an 11-year-old in Bangkok. "A letter from a kid halfway around the world. That kind of stuff is so amazing."

Mary Rothschild

"I've always loved children, I've always loved storytelling, and we had the space available," says Mary Rothschild, 51, explaining why she opened a children's center in her Brooklyn brownstone. In addition to running craft and storytelling programs for kids, she also gives educational workshops for parents. "Supporting good parenting is a real joy to me," Rothschild says.

After working for the U.S. Customs Bureau for many years, "this is the first job I've had that I can actually call mine and not something I'm doing for a paycheck," says Rothschild, who earns about $22,000 a year. "I am doing what I was meant to do."

Terry Joseph

Until he went to work for Big City Forest five years ago, Terry Joseph was on the street. "I didn't do much good stuff," says the 25-year-old. The company, which turns shipping pallets into fine furniture and street kids into skilled workers, hired Joseph out of a training program. Now he's a foreman, supervising about a dozen workers: "I feel pretty good when I see people who've come in not knowing anything and I've trained them." And Joseph says that, unlike some of the places where his friends work, at Big City he's trusted: "It's like a family."

Peter Mack

Although he's teamed up with girlfriend Kerri Mahoney to create Web sites for kids, Peter Mack, 26, says his "real focus" is creating CD-ROM entertainment and multiplayer online games. "People watch TV or movies to experience something they cannot experience in real life. The potential for that level of immersion is there with CD-ROM and video games -- only rather than seeing it happen to someone else, it can actually happen to you. That's incredibly powerful," says Mack.

He also likes the freedom the medium affords him: "With the Web or video games it's really in the hands of the viewer. You can push the envelope. People who are wired are the ones that appreciate that kind of thing."

Haojiang Tian

Growing up in China during the Cultural Revolution, Haojiang Tian would steal moments from his work at a factory to practice scales. Now, at age 40, Tian is one of the few prominent Asians in Western opera, playing featured roles at the Metropolitan and other houses worldwide. Recalling the day he arrived in the U.S. in 1983, he says, "I had only $35 in my pocket and I spent $8 to go to the Met and saw Pavarotti. I sat in this great opera house and looked around. It was like a dream." Ten years later, he was singing onstage with the opera star. "He held my hand when we took a bow. It made me cry."

Gilles Malkine

Gilles Malkine spent 20 reasonably content years as an architectural draftsman. Then a friend with Lou Gehrig's disease asked Malkine to design a larger, accessible bathroom for her. The favor led him to a nonprofit independent living center in White Plains, where he now designs accessible living and work spaces for people with disabilities.

"It changed my life to put this particular slant on what I do," says Malkine, 48. There are hurdles: "You are working with very limited funding and overpriced products in the disability market." But the rewards far outweigh the challenges. "I'm actually helping people," he says.

Cintra Pemberton

Sister Cintra Pemberton, an Episcopal nun, started leading pilgrimages to Ireland and Wales five years ago after she became excited by Celtic spirituality. "It was like a breath of fresh air for my own faith, and I wanted to introduce it to others," she says.

For the 60-something Pemberton, who was a music professor before she entered the order, the volunteer job is a natural extension of her teaching: "We do intellectual academic stuff, we visit holy sites, we pray together, and we have lots of plain old fun. It incorporates all aspects of who we are as human beings."

Keith Lane

Keith Lane, 48, is a bill collector -- and he loves it. As credit manager for a law firm, Lane spends 40 hours a week judging clients' creditworthiness and collecting bad debts. "I get to look at every aspect of a business operation. It's almost like doing a physical -- there are rules, but every person's a bit different. That makes it a creative process." The people side is equally stimulating, he says. "Nothing is more fraught with anxiety than money. It produces a kind of instant intimacy, and involves a level of honesty you don't experience day in and day out."

Phyllis Jenkins

Phyllis Jenkins, 66, was restless after retiring from a nursing career last year. "I visited every museum and every park -- I did all the retirement things," she says. Finally Jenkins went back to work part time, devoting 12 hours a week to a research project that tests whether ultraviolet light protects people with HIV from tuberculosis.

"When I first started working with people with HIV, most people, my family included, thought I was crazy," she says. "But I have benefited so much in my life, I felt this was a fitting way for me to give back."