I like to keep a notebook when I travel. Your camera can only capture so much, and you know how it is - "the pictures don't do it justice." With your notebook, you can capture more nuance and feeling, especially if you are in a new place full of new experiences and sensations. It's also a good place to jot down names and addresses of new friends and places.
Besides, you look much more dignified and thoughtful if you are sitting quietly on a bench or a rock, writing in your notebook, than you do when you are taking selfies and jump-shots.
I love taking a journal with me on trips! I usually get one with unlined pages so I can sketch things in it too. It’s pretty fun to sit around a campfire on your last night and relive memories with your fellow travelers.
You can't go wrong with a journal. A large part of the reason I love being in the outdoors/traveling is to find quiet and a bit of introspection. Writing when I'm hiking, camping, or traveling helps with that for me. Not to mention it seems that I have the makings of a terrible memory, so jotting down small details about directions, names of places, etc has been super helpful after I return.