Vacuum-sealed bags are always a good idea. You put clothes in the bag, then squeeze all the air out and tighten the plastic wheel on the side. In some cases you just squeeze the top shut like a sandwich bag. These bags help cut down on packing space and are great for long-term trips. Such as, say, going to England for 10 months to attend university.
Multi-plug adapters are priceless. My favourite is my blue box with US, UK, European and Australian plug options which can be pushed in or out with sliders. It looks vaguely like the Tesseract from The Avengers and has taken me just as many places. A lot of companies make these so you have many options.
Another great gift is anything that you can wrap wires around for safekeeping in transit. I have used and gifted Cable Turtles, Velcro wire straps and other similar products myself. These are useful when you have a lot of charger cords and earbuds to keep separate in a backpack.
While we're on the subject of technology, a good laptop case is essential for travel. There are plenty of nice ones that provide plenty of padding and even extras like pockets on the outside. Personally, I think padding is a top priority to protect the computer if it falls.
When traveling, normal clothes work most of the time but some activities require certain items. A good pair of hiking socks is always useful, whether for hiking or simply for days with lots of walking around. They are also very warm!
Some people like to keep journals while they travel. During my gap year, I took notes on the different foods I tried, made playlists and did funny creative stuff on train rides in a notebook. While not everyone writes, a small notebook is an excelleng gift for someone you know will use it.
Wherever the people in your life like to travel, basic travel essentials will almost always be appreciated for birthdays and holidays. Finding something in a favourite colour is a nice personal touch as well. Some of these items are obscure, but many are online - you don't have to travel the world to find them.