I've been a loyal Mac guy for almost ten years now, and I've owned an iPhone since 2008. I don't have a lot of cool aps for my iPhone, but there are a handful of aps that I take on the road with me when I travel. I'm sure there are plenty of other good programs for all the road warriors out there, but these are some of my favorites.
1. Tide Graph
This is a handy ap that gives you the tides of any location in the United States. You can track the tides and look ahead to see what they will be in the future. The graphics are very intuitive, and well laid out. Whenever I'm on Saint Simons Island, I use this ap quite often to let me know when it's paddleboard or fishing time. ($1.99)
If you're a Kindle person and you have an iPhone, you really need to get the Kindle ap. Kindle is a great way to read all your ebooks, and what's especially cool is that it automatically synchs between your other devices. For instance, if I read ahead on my iPad, when I open the same book on my iPhone it scrolls ahead to where I left off on the iPad-- very handy if you have more than one device. (Free)
3. White Noise
This ap is an awesome travel aid. I've been using this ap for the past year and have turned it on to help me sleep during the day after night shift, and also to listen to through headphones when I'm trying to focus in a noisy location (like trying to read in a public area). This ap generates a variety of background noises that are steady and soothing. My wife and I also use it to help the kids go to sleep when when in unfamiliar environments (like a new hotel room, etc...). Below is a video demonstrating this ap ($1.99):
I like Urbanspoon, and while I don't use the website or ap often, when I'm in a new city I've found both to be very useful. The ap is very easy to navigate and provides a lot of information very quickly. One of the best features is that this ap can use your location to find nearby restaurants and estimate the distance to each. Very useful for someone with limited time to grab a bite in an unfamiliar city. (Free)
These are the few aps I use routinely when I travel. If you have others, feel free to make suggestions.