By Katherine Nichols

It's 7 a.m. and you realize that you need to take out-of-town clients to dinner. You don't have a reservation, and you can't call at this hour -- no one will answer! You can leave a message, but then you might not discover until the afternoon that your restaurant of choice is completely booked. What to do?

There's a solution that sounds new, but actually has been around since 1999. The difference is that it's catching on like wildfire now. It's called OpenTable.com, a Web site that allows you to discover immediately which restaurants are available at the right time, make a reservation online and get confirmation within seconds.

The service began in gourmet-conscious San Francisco, with a rapid migration to New York City. According to a recent New York Times article, it took three years for the online reservations company to seat its millionth customer. Now it reserves tables at restaurants for 2 million people each month.

Ann Shepherd, senior director of consumer marketing for OpenTable.com, said that 800 eateries are registered in New York, and customers can choose from 600 in San Francisco. Hawaii has 41 online (23 on Oahu), which is "double where were at this time last year," said Shepherd.

"We're really anxious to grow our base of restaurants there," she said. "It's a unique market, with so many travelers. Visitors have the convenience of booking reservations online before they even hop on the plane."

Continued in Part II.