(FORTUNE Small Business) – Alfred Dominick knew it was time to switch travel agencies when, during a business trip, he found himself stranded in Newport, N.H., without a hotel room. Turns out the agency had booked him into a hotel in Newport, R.I. "I definitely was not pleased," says Dominick, 58, who runs InteliData, a Reston, Va., financial services company.

Add nightmare scenarios like that one to the rising cost of roadtrips, and it's no wonder U.S. businesses are increasingly avoiding travel agents. According to a March survey by Forrester Research of Cambridge, Mass., only 41% of U.S. companies use agents, down from 53% two years ago.

Companies that book their own travel online may avoid the high fees and occasional mistakes of a traditional agent, but other dangers lurk. Internet firms such as Expedia and Travelocity, for instance, are unlikely to save you money unless you're wise to cancellation fees and other intricacies of airline ticket pricing. That opens up a niche for tech-savvy agents who can help companies control their travel costs.

Dominick's company was lucky enough to discover MacNair Travel Management, an Alexandria, Va., firm that specializes in efficient business travel. Since May 2001, MacNair has reduced InteliData's average ticket price from $674 to $435, saving the company $535,738. That's a hefty sum for a firm that had 2003 revenues of $21 million.

"It's been night and day dealing with MacNair," says InteliData travel manager Vickie Hollowell. "They've saved us a lot of money and headaches." To find similar travel agencies in your area, call the National Business Travel Association (703-684-0836), which helps connect businesses with agencies. Or search the online directory of the American Society of Travel Agents at travelsense.org.

Mike Macnair, 42, started MacNair Travel with his wife, Ellen, in 1989. Business was good at first, with annual revenues averaging $2 million. But by 2000, U.S. airlines had stopped paying commissions to travel agents. And online travel sites such as Expedia and Travelocity had drawn a growing market of do-it-yourselfers.

The MacNairs decided to harness the technology that seemed to threaten their livelihood. Starting in mid-2000, they spent $100,000 on a faster computer network to reduce navigation time and facilitate information sharing among their five branch offices. They also trained their 25 travel consultants in the finer points of online fare searching. Searches that once took as long as two hours now average 25 minutes, including quality control to ensure that costs are in line with clients' budgets. All clients have 24-hour access to MacNair support staff.

None of his efforts will help clients, Mike MacNair cautions, if they don't establish sound travel policies and procedures. "We can offer low rates all day, but if travelers don't have to take them, the company won't save money," he says.

Many U.S. travel agencies went under after 9/11. Meanwhile, MacNair's revenues have been just shy of $3 million for the past three years. It helped that MacNair was already an established brand in the nation's capital, where word of mouth spreads fast. About 80% of MacNair's revenue comes from local businesses, such as the Bush-Cheney campaign. The average airline ticket price MacNair secured for those clients last year was $364.31 lower per ticket than the national average, according to a recent nationwide study by Topaz International.

Does Mike MacNair feel threatened by online competitors such as Travelocity Business? "Those big guys are the H&R Block of travel," he says. "If you just need a simple transaction, you are okay, but anyone with complex needs should go with a professional service provider."