1) Reusable water bottles and/or water filters

There's no need to waste money or natural resources by buying disposable water bottles with these nifty water solutions. Reusable water bottles are handy for everyday use as well, whether you're going to work, class, or are just running errands. Portable water purifiers, such as an ultraviolet light purifiers or packs of chlorine dioxide tablets are perfect for backpackers and anyone traveling in the developing world, where you can't always drink the tap water. There are even water bottles with built-in purifiers for the ultimate convenience factor!

2) Travel towels

According to The Hitchhiker's Guide to the Galaxy (Douglas Adams' cult classic novel), a towel "is about the most massively useful thing an interstellar hitchhiker can have." Well, that goes for adventurers on planet Earth as well -- from camping, to lounging on the beach, to a long day of city exploration, a towel can be an indispensable tool. Many hotels charge extra to rent towels for the beach or pool, and some hostels don't provide towels at all. Aside from the obvious uses, towels can also be used to shield your head from the sun, to cover a questionable-looking bus seat or hostel pillow, or as a cushion. Quick-dry, antimicrobial, and UV protective fabric makes towels like these a thoughtful and infinitely useful gift.

3) Solar charger

Break free from the grid! Use a portable solar charger to juice up your cell phones, mp3 players, and digital cameras. This gift idea is especially great for trekkers who might not even have access to an outlet for days at a time.

4) Compression packing bags

Originally designed for storage purposes, travelers have caught on to the convenience of compression bags for their packing needs. Pressure valves on these plastic bags suck all the air out, shrinking your clothes and other items to a fraction of their size to make the most of your suitcase/backpack space. But be wary of weight restrictions on flights, as the more items you pack into your bag, the more it will weigh.

5) Portable coffeemaker

No one wants a travel buddy suffering from coffee-withdrawal grouchiness! There are several types of portable coffeemakers, mostly geared towards campers, that are perfect for those who are only functional after their morning cup o' joe. Coleman makes a highly reviewed drip coffeemaker that can go right on a camping stove. There are also French press-style coffeemakers that come in a variety of sizes, including a portable mug that you can drink right out of as soon as your coffee is ready.

6) Travel apps

Why not buy your loved one a travel app or two for their mobile device? There are so many different kinds of apps for travelers out there, from games to prevent boredom on long flights to language translators. Other travel apps include trip itinerary organizers, currency converters, free Wi-Fi finders, flight alerts, and databases with maps of every kind (city maps, rail maps, park maps, ski resort maps, and more).

7) Basic medical kit

A lightweight basic medical kit can be crucial in a pinch. Get one that is small with a soft container that will fit easily into a purse or backpack. If you're not in a major city, chances are there aren't convenience stores on every corner. Simple items like Band-Aids, Neosporin, bug bite cream, antiseptic wipes, and over-the-counter medicines for common ailments (like minor pain, allergies, indigestion, congestion, and heartburn) will be worth their weight in gold if the situation calls for them.

8) Donations

Does your traveler already have all the gear they could ever want? Make a donation in your loved one's name to a nonprofit organization that is working to help a destination he or she loves. If they bonded with a local community, there are many organizations doing great work for underprivileged communities, such as helping children get an education, advocating for women's rights, protecting local wildlife, and promoting fair treatment of workers in the tourism industry. If your traveler was awed by the beautiful natural environment they visited, consider donating to an organization that is working towards preserving that special place!