Solo travel is a hot topic for the travel industry these days. Tour and Cruise companies alike are trying to make inroads in the solo traveler market. Many are allocating solo space, building solo cabins on ships, waiving solo supplements on certain tours and sailings, all the the effort go gain your business!
There are a couple of companies that I have a lot of respect for because they have ALWAYS honored solo travelers and design their itineraries, hotel space, etc. accordingly.
Most of the bigger tour companies offer promotions for waived single supplement on some tours. Most local or independent tour companies support solo travelers with no or low additional fees. For example, we use Killa Expeditions a lot for Peru.
For cruise lines, Norwegian Cruise Line has some ships with solo cabins. They are inside cabins, but a not too small. The cabins also have access to a solo traveler lounge, which is nice.
Royal Caribbean also has added solo cabins to Quantum of the Seas, Anthem of the Seas, Ovation of the Seas and Harmony of the Seas.
Most all of the large cruise lines offer either a solo cabin, a larger cabin they allocate for solo travel, or promotions waiving solo supplement fees.
Star Clippers does a nice job of supporting solo travelers. They allocate solo space on most sailings, waiving the solo supplement fee.
Celestyal Cruises also does a nice job, as many of the smaller, more local, cruise lines support solo travel.
All of the river cruise lines offer solo cabins as promotions, meaning, some sailings, some ships, with limited numbers available.
Here are some great articles if you want to dig deeper.