I'm a bit of a contrarian about holiday gift-giving for travelers. You see loads of lists that focus on some combination of gadget "stocking stuffers," travel clothing, luggage, accessories and such. My take on those is that most travelers already have the gadgets and accessories they really want, and most of those stocking-stuffer travel gifts quickly become "drawer stuffers." Ditto luggage, clothes, money belts, passport and credit card wallets, chargers, foreign plug adapters and similar items. I'm also excluding "cash equivalent" travel gifts -- buying something the recipient has already specified as wanting, paying part of an upcoming trip, buying a railpass, a gift card or otherwise making what amounts to a direct cash contribution. That's certainly OK, but it doesn't really count as a gift in the holiday sense. Given that introduction, here are some ideas based not so much on things as on travel, itself, and enhancing the travel experience.
If your traveler already has a trip planned, with specific dates and places, consider arranging some destination activity you know the traveler will enjoy. If your traveler is a baseball fan and heading for Chicago, for example, get Cubs or White Sox tickets. If your traveler is fond of theater, arrange tickets to a show in New York, London or Vegas. Depending on musical tastes, check to see what's on in a primary destination: rock concert to jazz to symphony to opera, you can probably find something that fits. For someone headed for a resort, consider a spa treatment. If you know the specific itinerary, you might arrange a VIP "meet and greet" and limo transfer at a destination airport. If you know a destination hotel already reserved, see if you can organize an upgrade to a suite. You get the idea: Arrange some extravagance -- petty to major -- that you know the traveler would enjoy but probably hasn't already arranged.
If your traveler has no immediate travel plans, consider something that could enhance the experience just about anywhere, anytime. I have two primary choices here, each with a lot of flexibility. My number one choice, at least for a traveler who already isn't in a program, is to enroll the traveler in a program that provides access to lounges at airports. Lounges provide an oasis of calm and comfort in a big airport's otherwise hostile environment -- along with a no-charge spread of snacks and beverages. For some travelers, the best buy might be membership in the lounge program of the individual airline you know your traveler flies most frequently. This is a big-dollar item: On a major line, typical lounge membership is $495 to 550 per year; less on smaller lines. A more flexible option is Priority Pass (prioritypass.com), a program that provides access to a wide range of lounges -- a mix of airline and independent. Annual membership costs $429, with unlimited no-charge visits to more than 1,200 lounges and airport restaurants, worldwide. Priority Pass coverage is generally better overseas than in the U.S., but U.S. coverage is improving. If annual membership is a bit beyond your budget, LoungeBuddy (loungebuddy.com) arranges one-time lounge entry at a worldwide network, starting at $25 for a visit.
My other primary choice is to give an actual trip. You can do that in a number of ways, but perhaps the easiest is to buy a hotel-stay coupon from Groupon (groupon.com) or Livingsocial (livingsocial.com/travel), which usually covers a two- or three-day stay at a leisure-oriented hotel or resort. You can find lots of options for less than $100 per night for a couple. The big advantage to these coupons as gifts is that they're typically valid for a period of several months, so you don't have to try to guess your traveler's exact schedule. You can almost always find something within easy one-day driving range from about anywhere in the U.S. or you can concentrate on one of the popular destinations such as Las Vegas or Orlando.