Many people prefer traveling alone, and for independent travelers, solo journeys offer infinite opportunities to make friends and meet locals. Unfortunately, the travel industry is geared toward couples, so singles often wind up paying the penalties of traveling alone (like supplemental room fees) if they don't know how to avoid them. Single travelers can avoid these supplements, of course, by agreeing to room with other single travelers on the trip. An even better idea is to find a compatible roommate before you go from one of the many roommate-locator agencies.
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.
Many reputable tour companies offer singles-only trips. Singles Travel International (tel. 877/765-6874; www.singlestravelintl.com) offers singles-only escorted tours to places like London, Alaska, Fiji, and the Greek Islands. Backroads (tel. 800/462-2848; www.backroads.com) offers "Singles + Solos" active-travel trips to destinations worldwide.
For more information, check out Eleanor Berman's classic Traveling Solo: Advice and Ideas for More Than 250 Great Vacations, 5th Edition (Globe Pequot), updated in 2005.