Like many companies, Door Number 3, an Austin-based advertising agency, has been feeling the effects of the recession. In the past year and a half, several of the firm's long-term clients have reduced their advertising budgets. Because business was slow and employees were idle, M.P. Mueller, the company's president, decided to ramp up the agency's pro bono efforts. "We have such a great team, we didn't even want to think about the l-word," says Mueller. "So we sought out some bigger pro bono projects that would keep the creative juices flowing."

Taking on pro bono work has long been a way to establish a track record and build a portfolio of work. Donating company services also helps keep employees sharp and motivated between projects. Mueller, for example, set her staff loose on several unpaid projects for nonprofits, including Habitat for Humanity and the Austin Humane Society. She estimates that this year, her 15 employees have donated a little more than 10 percent of their work hours to nonprofit organizations, nearly twice as much as they did before the recession.

These sorts of projects don't help only charities, which have lately seen donations fall. Mueller says they also help employees create some of their most inspired work. "You get a lot more freedom with nonprofit clients," she says. Rallying around a cause -- and creating work that you are proud of -- can be incredibly rewarding. "If our talent can continue to do meaningful work, then they are not going to be searching for something else," says Door Number 3's creative director, Prentice Howe.

Doing unpaid work for nonprofits can also lead to more paying customers, says Giacomo Guilizzoni, founder of Balsamiq, a Sacramento-based company that makes software for Web designers. Guilizzoni's own pro bono efforts were born when he realized he didn't feel comfortable taking money from nonprofits. Shortly after the company launched last year, Guilizzoni decided to offer free software licenses to all nonprofits. More than 2,400 free licenses later, valued at some $680,000, his four employees spend 15 percent of their time on work for nonprofits.

It makes more business sense than you might think. Guilizzoni says his paid business has grown at the same rate as his charitable donations. "A lot of people who volunteer at nonprofits work for companies that aren't nonprofits," he says. For instance, one recipient of a free license built a website for an orphanage in Honduras in his spare time. He eventually demonstrated Balsamiq's software to his employer, which bought five licenses. Balsamiq's annual sales recently exceeded $1 million, a milestone Guilizzoni credits to the boost his software received from his nonpaying users.

When taking on pro bono work, it's important to treat your nonprofit clients like any others, or things could go sour. Mueller suggests clearly mapping out the scope of any project. Setting expectations in advance will help ensure that neither party feels slighted or overworked.

Mueller also recommends getting to know the organizational structure of the nonprofit to determine who is responsible for making decisions. Some nonprofits have many layers of bureaucracy. Mueller learned that the hard way. When working with one charity, she says, Door Number 3 completed a campaign to the specifications of the executive director, only to have the board of directors demand another time-consuming and costly photo shoot.

Keep in mind that beggars can be surprisingly choosy. Sometimes companies have to draw the line about what nonprofits can get for free. Newfangled Web Factory, a Carrboro, North Carolina, Web design firm, lets its employees work on pro bono projects of their choosing during slow times at work. Most of the projects consist of designing and building websites, which are then hosted on Newfangled's servers.

These ongoing relationships, in which the charity becomes reliant on Newfangled's continuing service, have led to some problems. Occasionally, one of the nonprofits the company helps will undergo a reorganization, and the new staff will want to revamp its website. "They'll get in touch with us and want to make a whole lot of changes," says Chris Butler, Newfangled's vice president. When the requests are too great, Newfangled politely but firmly says no.

Despite the occasional challenges, pro bono work is definitely worthwhile, says Howe of Door Number 3. "You've gotta believe in karma."