I really like the hotels.com app. It's simple and fast to find and book hotels. They have a terrific rewards program where if you collect 10 nights you get the 11th for free.
If you're spending any length of time in a location consider renting a home through Airbnb. They now have a section for experiences where you can do fun things like spend an afternoon on a sailboat.
Kind of a one stop shop for booking a trip. Check out their things to do tab where you can see activities and excursions available in your destination during the dates of your visit.
Another site where you can book everything, flight, accommodation, rental car. Known for their Express Deals where you can book a last minute hotel at up to 60% off, but they won't tell you which hotel until after you book.
I keep this app on my phone too and always check both the Booking and Hotels apps when I'm planning a trip.
For all-inclusive trips.
When you're staying in a city and can mostly rely on transit to get around, Uber makes more sense than a rental car. I'm super excited that Uber is FINALLY coming to our city - Vancouver. I've used it in my travels in the US and it's always been a great experience, though I was super annoyed that both Uber and Lyft drivers jacked their prices through the roof when BottleRock Napa shut down in the evening. It felt gougy.
Avis Rent A Car
I've always had great experiences with Avis.
Thrifty Car Rental
Because it's a good idea to do a price compare. In fact, several of the sites mentioned above let you check car rental prices.
ViaRail - Canada
A few years ago my parents traveled across the country by rail in a super luxury car. I'm still jealous. Vivi and I have taken ViaRail between Toronto - Ottawa - Montreal.
Amtrak - USA
We can get on the Amtrak in Vancouver and ride down to Seattle or Portland. Check out Derek Low's tale of going coast to coast on Amtrak for under $200.
I haven't traveled by rail in Europe for over 20 years, but I know it's still the best way to get around. This site offers great promos and has a planning tab that is helpful.
Airport Parking Reservations
When you've asked friends and family one too many times to drop you off at 0 dark 30. This site will save you money.
Get honest, recent reviews of just about any place you're considering visiting.
Here you can get expedited visas.
International Travel Insurance
World Nomads is a well regarded provider of travel insurance.
Tugo Travel Insurance
For travel to the US, I get annual coverage for Vivi and me. We travel to the US several times a year, but we also live on the border so we cross nearly once a week to pick up mail and we'd be screwed if we were injured and not able to get home to be treated.
The Secret Traveller
This is another insurance site, but they have a section called the secret traveller with great travel insights.
If you're looking for white water rafting, skydiving, or a themed tactical adventure in Las Vegas, this company has it all. You can search by experience or by city.