For true solo travelers, the sad fact is that much of the travel industry is geared toward couples. Standard pricing for tours and cruises is "per person, double occupancy" (PPDO), and anyone wanting to travel solo incurs a stiff "single supplement." For the most part, industry structure determines which specific travel services get priced individually and which are priced PPDO:
Hotel accommodations. Solo hotel rates are a mixed bag. Most modern hotels build all their rooms for at least double occupancy, with queen, king or twin beds, and often double-queens. A few hotels, however, have some small rooms designed for solo occupancy, although finding them isn't always easy. When you try to look at hotel rates through a big online travel agency (OTA), the default pricing is PPDO, even if you change the inquiry to one person. Overall, this doesn't make much difference, because in the vast majority of cases, the single and double rates are the same. It can get tricky, however, when you look for solo rooms in areas where room rates traditionally include breakfast. Fortunately, for an upcoming trip to Europe, I found that Booking.com and Expedia, among others, were pretty good about differentiating single and double rates.
But you're out of luck if you like to cut hotel costs buying through an Opaque OTA such as Hotwire and Priceline. Typically, they do not distinguish single and double rates -- in fact, they don't even indicate whether their "blind" rates include breakfast or not. Similarly, the various flash sale OTAs and promotional coupon deals always price double occupancy and give you no single option.
Cruises. A few cruise ships actually have single-person cabins, but most put solo travelers in a conventional two-person cabin and slam them with the dreaded "single supplement" that can often double the price. Although they occasionally offer promotions featuring reduced single supplements, try to find them! No big online cruise agency I checked for this report offered solo pricing -- even on the Norwegian Epic, a ship that features cabins for solo travelers. When I asked my colleague Carolyn Spencer Brown, editor of Cruise Critic, about the best way to find solo pricing, she responded that the only practical approach is to contact a travel agent, either local or online. She also noted that on the Cruise Critic blog, a thread at boards.cruisecritic.com/showthread.php(QUESTIONMARK)t(EQUALSIGN)851324, posts recent reports from readers about solo rates.
Tours. Although most conventional tour packages are priced PPDO, agencies such as Single Travels International (singlestravelintl.com) list a small number of solo-accommodations tours. But solo deals without a single supplement are hard to find: Even Club Med, the epitome of destination resorts for "swinging singles," prices on a PPDO basis.
The rest. Rental cars, taxis and such, are inherently biased to groups of up to four. The best bets for solo travelers are shared-ride shuttles for airport access and public transit.
(Send e-mail to Ed Perkins at eperkins(at)mind.net. Perkins' new book for small business and independent professionals, "Business Travel When It's Your Money," is now available through http://www.mybusinesstravel.com or http://www.amazon.com)