Back in October 2010, I had a great opportunity to travel the country with JetBlue's all-you-can-jet pass. My iPhone became my most trusted travel companion. I found that I used certain iPhone apps daily to help me.
One app that I used on a daily basis was Google Maps. Being in a new city every 2-3 days I need to know how to get around. Google maps was so good in giving directions on public transit. It say where to get off and then which bus/subway/train/streetcar to take next. It would give the times the next transit would show up at the stop but I found that to not be accurate most of the time. However just being able to use GPS to locate where I was, then type in where I wanted to go, I could have directions in a snap. Also using Safari and searching for where I wanted to go it would bring up the address and a button to show it in Google maps. Then I could get directions quickly that way too. It also gave walking directions and the estimated time it took. I rented a car a couple times and used it to get me around Denver and Portland, ME.
Another one I used almost daily was Yelp. This is one way I used it. I'd be walking and I see a restaurant that looks good from the outside or serving a type of food I was craving. I'd open up Yelp, type in the name, and see the listing. Then I could quickly see the overall star rating of the restaurant and quickly read some user reviews. If I had gotten lukewarm reviews (3 out of 5) stars, I would pass and move on. If it had lots of reviews (100+) with favorable ratings and after reading reviews it sounded like a good place, I would stop in to eat. I wanted to spend my money on good food and not have the mentality of trying out this place because this would be my only time to eat there. I love to eat food when I travel so that's what I look for.
I would use it also to just search for say "Ice cream" in the Boston area. It would give a list of the most reviewed ice cream stores and also the distance from my location. If I liked one, I would bookmark it. This was a feature that truly helped me out. At a later time, wherever I was, I could go to my list of bookmarks and it would show based on where I was, the closest place to me that I had saved. So when I was ready for some ice cream, I'd look at the bookmark to see if it was nearby wherever I was or to see how far away it would be. If it was close, I could click on a button to open it up in Google maps and search for directions from where I was standing.
I also used it for a boat tour once in Chicago. I stumbled upon it and noticed it was just boarding. I did a quick Yelp search and found the listing and saw it got rave reviews. I bought a ticket, and took a boat tour of Chicago. It was well worth the money. Now if there wasn't many reviews, old reviews, or bad reviews, I would have passed.
I used it to find a barber shop in San Francisco. I didn't want to just walk into some place. I passed on many when I read some reviews about the service. Again I was on a tight budget for the month and wanted my money to be spent well. I did find a nice one eventually.
Some other ones I used daily
Camera - I took more pictures with my iPhone than my regular point and shoot.
Skype - Used it to talk to my girlfriend who lives overseas. Being able to use it on 3G, meant I could be anywhere in the city and could talk with her.
Without these four apps, my trip would not have been as easy to plan and navigate. Looking forward to finding new apps that I can use on my next trip.