As a smart phone user I have gotten accustomed to using some great Travel App's all of which are free that I wanted to share with my fellow Insiders.
Marriott - With the Marriott application you can check rates, make and cancel reservations, and access your rewards account.
TripIt- This application allows you to create travel itineraries by forwarding your e-mail confirmations (e.g. hotel, airline, rental car) to TripIt and it puts your itinerary in order for you. It's nice not having to print out e-mail confirmations or searching through your e-mail box for the information. You can also share your itinerary with other TripIt Users. http://www.tripit.com
TripAdvisor - This application is useful for reading hotel and restaurant reviews. The feature I find most useful about this application is locating restaurants when I'm on the road. The application makes use of your phone's GPS and can list restaurants or hotels by proximity. You can then read the reviews and see which restaurant or hotel may be of interest to you.
Delta- If you fly Delta this is an excellent application. It allows you to keep track of everything associated with your flight including schedule & gate changes. If i'm taking a lunch break between flights I can check the application and verify if my next flight is still on time and/or if the gate has changed. This also comes in handy if you have a connecting flight and your original flight getting to the hub was delayed so while you are waiting to get off the plane you can check to see which gate you need to head to without having to check the screens in the airport. The Delta application also allows you to keep track of your checked baggage. Sometimes before takeoff I'll check and verify that my luggage made it on the plane.
GasBuddy- I think almost everyone has heard of this application. It helps you locate the lowest gas prices in the area. Helpful at home and when your on the road!