On package vacations, single travelers are often hit with a "single supplement" to the base price. To avoid it, you can agree to room with other single travelers or find a roommate before you go.
Travel Buddies Singles Travel Club (tel. 800/998-9099; www.travelbuddiesworldwide.com), based in Canada, runs small, intimate, single-friendly group trips and will match you with a roommate free of charge. TravelChums (tel. 212/787-2621; www.travelchums.com) is an Internet-only travel-companion matching service with elements of an online personals-type site, hosted by the respected New York-based Shaw Guides travel service.
Singles Travel International (tel. 877/765-6874; www.singlestravelintl.com) offers singles-only escorted tours. Backroads (tel. 800/462-2848; www.backroads.com) offers "Singles + Solos" active-travel trips to destinations worldwide.
Also check out Eleanor Berman's classic Traveling Solo: Advice and Ideas for More Than 250 Great Vacations, 5th Edition (Globe Pequot), updated in 2005.
Note: This information was accurate when it was published, but can change without notice. Please be sure to confirm all rates and details directly with the companies in question before planning your trip.