I use these apps both professionally and personally throughout my day. I hope you find them as useful (and fun) as I do. Here is my list in alphabetical order.
Dropbox - Most everyone already knows about Dropbox. It has become the leading cloud service for synchronizing your files on almost every computing device you own. This includes your iPhone and iPad. I keep all my active project files in my Dropbox folder. Any changes I make are reflected on all my devices. I can do office work on my home computer without bringing my laptop back and forth. And the ability to access and share a file from your iOS device has saved my bacon on more than one occasion. Navigate to a file using your iPhone, and send a link to that file to someone who needs it asap.
Evernote - Yes, another cloud service that most of you have already heard about. I use it constantly to capture notes that then appear on all my computers. With the iPhone app, you can also create notes that are snapshots from the phone's camera or even voice recordings. Evernote will even do OCR (Optical Character Recognition) on images files you add to your notes. The beauty of this is that you can later do text searches, and images will be included in the search results.
Fandango - Want to go to a movie, you have everything you need in your hand. Find nearby theaters which you can see on map and get directions to. See show times and even watch trailers. And for certain theaters, purchase your tickets ahead of time from your phone. I've used this and MovieTickets numerous times on business trips when I had a spare night with nothing to do.
Fieldrunners - This is a great game which is available both for the iPhone and iPad. Your objective is to place various obstacles on a field of battle to prevent an army of little soldiers from reaching the other side. There is a variety of soldier and obstacle types. Combined with a near infinite way to arrange them on the field, this creates a game that always finds a new way to challenge you. It definitely requires some strategic thinking.
GoodReader - This is a fantastic iPad application for viewing documents of different types: MS Office, PDF, and image files. It even provides great tools for marking up documents with shapes, curves, and text. I even use it to put my John Hancock on PDF documents which I can then email. This is way more convenient that printing/signing/faxing. When off to one of my kids lacrosse tournaments, I can load rosters, schedules, and field maps. And the annotation tools allow me to highlight those things I must find at a glance. GoodReader along with Evernote has allow me to almost never print a piece of paper.
GPS Drive - This GPS app is as full featured as most Garmin and TomTom devices you can buy. Integration with the rest of you iPhone, like contacts, makes it even more versatile. I've used it on business trips when I didn't have another GPS, and it worked great. When packing light for a trip, all you need to bring is a car mount for your iPhone. To get turn-by-turn directions, it is an ability that is actually an in-app purchase. For $10/year you get this feature, which also includes traffic alerts.
Houzz - I really appreciate great architecture, and I hope to one day build my right-sized dream house. This app and online service impresses me all the time with great images of beautiful homes. It is packed with images of homes, landscaping, decorating ideas, and home products. The images and descriptions are provided by architects, landscape and interior designers, along with home product companies. The images are thoughtfully organized so it is really easy to find what you are looking for. You can even tag photos which are added to your own idea book.
Kayak - When arranging for travel, the number of flight and hotel choices is dizzying. How do you wade through 75 flight choices to find the best one for you considering price, schedule, and convenience? You use kayak, that's how. It will search all the major travel sights for you and then consolidate the results to eliminate any duplicates. But wait, it gets better. It then provides you with an interface with handy sliders which allow you to quickly filter the results down to your ideal choice. Move a slider for departure time, and in real-time, you see the choices quickly reduce down. Even when I must use the company's selected travel service, I always start in Kayak to quickly identify my best travel options.
MindNode - If you are someone that knows me, or have read my blog, you know that I am crazy for mind maps. I use them all the time. Whether it be to clear my head, explore ideas, take notes, or brainstorm; I almost always have a mind map open on my computer. The application I use is MindNode. On the Mac, it is fast and simple to use. There are also versions available for the iPad and iPhone. Mind maps I create on the go are easy to send to my desktop version of MindNode. Want to share a mind map with someone that does not have the app, no problem. It provides a very convenient way to send image or PDF files.
MovieTickets - Though the user interface is different than Fandango's, the two applications offer near identical capabilities. I have both on my iPhone since you can buy tickets for certain theaters in Fandango, and different theaters in MovieTickets. By having both, I have most theaters covered.
OpenTable - What a fast and easy way to find somewhere to eat. Search by location, restaurant type, and preferred dining time. Options are presented in a list or on a map. Explore each restaurant to see how they have been rated by other diners, though I take most reviews with a grain of salt. Find a restaurant you like, lock in your reservation right on your phone. I have found this app useful both near home and while away on business trips.
Penultimate - Need a notebook to actually scribble in? With this app, you can draw in a handful of colors and line thicknesses. You can even place a photo in the notebook and draw over it. There are a lot of sketching apps on the iPad. What I like about Penultimate is that it is fast, easy to use, and has a very light user interface. Most importantly, the line quality and behavior when you draw is better than just about any other app out there. Sketching apps work best when you use them with a stylus, such as the Bamboo Stylus.
Plants vs. Zombies - This is another fun game for people who like games oriented towards strategic thinking. Use different kinds of plants to prevent a horde of zombies from entering your house. As the game progresses, new zombie types increase the game's difficulty. This is a great distraction when you have 15 minutes of down time at the airport or while waiting to pick up your kids from practice.
SoundHound - You've been there ... your driving and a song comes on that you can't remember the name or artist. Or it is so good, you want to remember to buy it later. Tap the big button on the SoundHound screen and it listens to the song being played. Moments later, it will tell you everything you wanted to know about that song. It will even play a clip for you to confirm that it is the right song. It can get you the lyrics, find similar songs, and even buy the song for you in iTunes.
Starbucks - I never worry about having money when I go to Starbucks for my favorite drink, a non-fat vanilla chai tea. I have this app set up to auto-reload my account every time my balance falls below a certain amount. When buying your drink, just hold your phone up to the scanner and your drink is paid for. I really doesn't get any easier.
Things - This is a To Do app that follows the productivity techniques of David Allen, described in his book Getting Things Done. If you buy into the process, it is a great way to empty your inbox and reduce the chances of forgetting to do things. Be warned, it does take a bit of discipline. My To Do list is synchronized between my computer, iPhone, and iPad. I have been using this for years now, and it has served me very well.
Tripit - My absolute favorite feature of Tripit is that you can email the trip itinerary (which you get from Expedia, Travelocity, and the like) to email@example.com, and it magically parses it. It just about always correctly identifies your flight, hotel, and car information which is then entered in the correct fields in the app. I never have to manually enter the details of a trip. I have a pro account, so it tracks my trip and let's me know if there are any problems like delayed connections. With the iPhone/iPad app, you have not only your trips itinerary easily accessible, but you also have all your frequent travel information. Account numbers, accumulated points (automatically updated), and important phone numbers. Don't leave home without this service and app.
TuneIn Radio - I'm a big fan of NPR, but I'm not always at a radio. This app lets me listen to radio anytime and anywhere from my iPhone. When traveling, you can even bring along your local favorites from back home. Hundreds of stations are available and are organized by location and genre. It even acts like Tivo for radio. You can pause and resume live broadcasts. You can even schedule it to record the same show everyday to listen to at a later time. Combine this with blue tooth speakers like the Jawbone Jambox, and you have a very nice setup for radio listening.
Zinio - I've been slowly letting my traditional magazine subscriptions run out so that I can instead subscribe on my iPad. Zinio has hundreds of magazines available and the subscription cost is comparable to what you would pay for a paper magazine. I would rate the reading experience as pretty good by iPad standards. It works well, but you know the iPad is capable of so much more. You can still easily navigate pages and zoom in on pictures. You can also bring up text only views for easy uncluttered reading. Apple's Newsstand has a ways to go before it can compete with this. Its magazine selection is small, and the prices seem to be pretty high.
Zombie Gunship - Hmm, what does it say about me when two of my three favorite games are about battling zombies? In this game, you're safe in an airplane at altitude as you "bring the rain" down on the zombies who wish to invade your base station. Blast the zombies, protect the base, and save wandering humans. But be careful not to kill those people running past zombies who are trying to reach the base for safety.
[Editor's note: This was originally posted on Rick's peronal blog, Absurdley Ideal.]