Trip Advisor- http://www.tripadvisor.com
Before you go research hotels, restaurants, and things to do when you get there. I love to read the comments, because sometimes a review from another mother can tell you more than the number of stars!
Really great app for your phone. If your in a strange city and you need gas, a grocery store or McDonalds french fries you can search and find it fast. It will give you directions and reviews. We were looking for breakfast in San Francisco and it helped us find a quaint coffee shop.
Spot Hero- http://www.spothero.com
Traveling in Washington DC I fell in love with this app. If you want to find parking in a big city, plug in your area and parking spots pop up. You can reserve a spot on your phone, pay for it, and then use your spot later. We got a great spot in Washington DC across from the White House for $9. When we arrived the next day the parking lot was full and we told the attendant we had a reservation, he parked us right away. I noticed the price for all day parking was $17, and I payed $9 with the app.
My husband loves Priceline, he uses it for hotels and rental cars. You can accept their price or you can name your own price. He starts his price at 60% and slowly adds to his bid until it gets accepted. He gets really excited when he can get a rental car for $19 a day.
We used Uber in California and Florida! It is a great app for your phone when you need a ride. You search in your area and enter your number of passengers and where you are going. A Car will accept you and send you a photo of your driver and type of car. The best part is your credit card is billed (you select tip ahead of time) and an emailed receipt is sent to your phone. No money changes hands!
I hope I gave you something new you can use!