Look at what they would consider a traditional gift, and try bringing them something they cannot get easily. You don't say what country you would be visiting, but there is a lot of information ion the internet, if you do a search on "traditional gifts" and the place to which you are going. That should give you an idea. Look up "taboo gifts" as well- because something like a gift of goats milk soap could be seen as a luxury or an insult...

What do they like? What ages are they?

Sports t-shirt/merchandise from pro teams

Art work.form local artist. A small photo, painting of a local pond. mountain, forest area or monument by where you live.

A book about the town you grew up in. Small maps of the area.

It really depends on what interest your friends. Do they collect anything.

My friend collects rocks that are specific to an area. He has them in his backyard decor.

I have a small framed photo of London my friend took from their apartment window. I love it and have had it for years

You can go to your local public library or town hall to ask what is unique to your area. Tell them you are looking for a gift for international friends. Town hall would know of businesses in your area that may have local artist or products.

which country? Japan, for instance LOVES higher end food items like regional specialties( think maple syrup or maple sugar canes from New England for instance).

is your area known for anything?

Something from YOUR area.The local special thing.

Maybe a thoughtful book or something hand made?