Viator--which is the Latin word for traveler--sells its products directly to consumers and through its global network of more than 3,500 affiliates that include major hotel and airline companies, online travel agencies, city-specific sites and more. The San Francisco-based company provides access to more than 5,500 tours, attractions and activities in 400-plus destinations in 75 countries.
New York-based Travel Ad Network reaches users through Web site publishers including BBC's Lonely Planet, Rand McNally and 50 other travel Web sites.
--Tanya Irwin