I have to say, I feel very lucky to travel in a time where technology is so big. Having a hand held device that gives you directions, translations and extremely accessible booking makes travel a breeze. Although, I could be up for a challenge (one day) to use a paper map and see where that gets me. There are SO many travel apps you can download before your trip, I've narrowed down the ones I use the most:
TripIt
TripIt is for those that are planners like myself. It shows your entire itinerary where you can insert lodging, transportation, activities, flights, dining reservations, everything! You can also invite your friends to take part so you both have a copy of the trip.
GetYourGuide
Get your guide is a tour hotspot. Type in the country or city you are going to and it will give you a list of 100+ tours in the destination you're heading to. I've found so many unique experiences using this app that I probably would've had to hunt for. They also have great cancellation policies incase you change your mind. I used it for a wine tour in France, a glamping experience in Colombia and just recently booked it for a Sahara tour in Morocco and a Petra/Wadi Rum tour in Jordan!
TravelSpend
I like to consider myself a 'budget conscious' traveler, however sometimes I do need to see with my eyes how much money I have left in the travel bank. Type in your budget for the trip and as you travel you add in every single expense you have, even if it is just a $2 coffee. You can also set up a daily budget to make it easier to stick to. Nothing worse than having to go into debt or your savings to finish up your trip!
Airalo
Airalo sells E-Sims for your phone! Buy a data plan for the country you are going to (yes you keep your same number) and don't worry about any of the roaming charges that you would otherwise have to watch out for everyday! They sell data plans for as cheap as $10 for a month.
HostelWorld
HostelWorld is where I book about 80% of my accommodations. Whether you like to stay in dorms or private rooms this shows it all in one place. You can read reviews of other traveler's and see the ratings for specific things (security, location, cleanliness, etc.) I always book with the option to cancel just incase my plans do change!
Rome2Rio
If you're looking to go from A to B but want to see which option best suits your budget. You can type it in Rome2Rio and it will give you prices for trains, planes, cars, ferries as well as the link to buy the ticket.
BlahBlahCar
BlahBlahCar is a ride sharing app in Europe. If you want to get a cheap quick ride somewhere, type in your destination and see if anyone is heading the same way (similar to Uber)
GoogleTranslate
I would have not gotten through France without this app. Pre-download languages so you don't need wifi and use it to look at menus, or to write out a sentence or to even just listen to someone.
I'm sure there are many more apps that I haven't mentioned/heard about but these are definitely the ones I use EVERY TIME I go somewhere!