Here are some of the ones I use most, amongst others....

JotNot Pro - A fax machine for your phone
Skype -
ScanLife - QR reader

If you got a 4S, be sure to turn on a security code and change the Siri setting to require the phone to be unlocked. Otherwise, anyone can use Siri to send texts, emails, and make calls to people in your address book.

Get a better weather app. I use the one from Weather Channel.

If you eat out, get Open Table.

Get the Trip Advisor, which has some great "what's near me now" features to find restaurants and other attractions.

Many banks have an online banking app.

Red Laser bar code reader can scan a bar code and give you prices for it and where you can buy it. Handy if you're at the store and wondering if something is a good deal.

Amazon has an app that can take a picture of something, identify it and give you a link to it on amazon. That might sound like you would just look at stuff in a store then buy it on amazon, but I find that's not the case. I look at reviews and check prices, but still often buy in the store.

Amazon also has a kindle app. Synchs between your kindle, if you have one, though the kindle is the weak link in that process. You have to be careful to get the kindle to send up your current reading location or the iPhone (iPad, pc version, etc) will lag behind.

iBooks is the reader on the iPhone.

I use goodreader on my iPad all the time. Haven't tried it on iPhone, yet, but appears to work there, too.

Between the iPhone and especially kindle and iPad I rarely read a printed book or document anymore. You can get pdf files to the devices in various ways, including several services. We have a "webdav" collaborative environment at my day job, so I can use that in combination with goodreader to store documents and books. We provide all of our documentation in pdf format and some in iBooks format, so I can have lots of documentation at my fingertips. If you manager your RE docs in a similar fashion, you could have all your contracts, offers, etc. all on your phone.

On my iPad I use Pages all the time, and Keynote and Numbers occasionally. Just upgraded to 4S from my ancient iPhone 3G, so haven't tried these yet. I have done customer presentations with my iPad and Keynote and the 4S is essentially the same hardware. Pages is great, and I use that for all my note taking. Numbers is obtuse and I struggle with that. Maybe I just need to make a concerted effort to figure it out, but it doesn't pass the "simple to use" test in my book.

A good app if you do any traveling is "AroundMe" - it does pretty much what it says, which is show you what's around you broken into categories.

I agree with Jon on the weather app. I tend to have both the Weatherbug app as well as the one from the Weather Channel. Both are good, but I've noticed the Weather Channel one, if left on in the background, will suck a battery down in short order.

A couple of my favorites are:
* Fandango- great for finding movie theatres, what is playing and even purchasing tickets
* Trip it- automatically creates itineraries when you recieve email confirmations for plane tickets, hotels, etc.
* Cam Scanner- uses your phone to scan paperwork for email
* NPR News/BCC- my two favorite news apps
* Pandora- radio
* Bank/Brokerage Apps

Oh, I forgot Dropbox which gives me access to my entire real estate filing system all the time! This has come in handy more times than I can count.

I give a strong 2nd to James on Dropbox. It is amazing. I can access all my info from my phone, iPad, or computer all the time and you can share selected folders with people if you want (I have different partners on deals that I share folders with, spreadsheets, etc).

Great thread!

I like Poynt for locating retail things and get ratings.
I am not a fan of the GPS on the Iphone, so I downloaded telenav, it was free and a much better GPS application

Good luck and thanks for the info!

What Jon said about having a security code applies equally to all phones, not just the 4S. I have an iPhone 4, and if anyone got their hands on it, they could call, send texts, etc. But it's always with me, so I don't bother with a security code. Anyway, I don't see why the 4S and Siri merit a special warning...?

Some of my most-used, non-game, third-party apps are Dropbox, Facebook, Echofon (for Twitter), Mint.com's app, Trulia, Foursquare, The Weather Channel, imdb, iQueue (for Netflix), Kindle, and Simplenote.

Yes, you're correct that the security code applies to all iPhones. Saying "it's always with me, so I don't bother with a security code" is equivalent to saying "I don't have a PIN number on my ATM card, its always with me." Its not a problem when its with you, its a problem when you lose it or someone steals it.

Siri merits a special warning because by default its insecure. Even if you turn on a security code, and I STRONGLY recommend EVERYONE do this, Siri will still respond to requests when the phone is locked and let anyone use the phone for any number of actions.

I agree with many of the above and here are a few more:

Realtor.com I like the "nearby homes for sale" feature and also drawing a circle on the map to find properties or comps.

Loopnet for commercial also has a properties near me feature.

The Amortizer.

Compoundee

CraigsPro for Craigslist.

Evernote - keep notes/pictures sync'd between PC/ipad/iphone
logmein - control your desktop PC remotely
mindmeister - mind mapping software
find iphone - lets you track your iphone if stolen
informant - syncs google calendar and has a very powerful task system. Use this daily.
pandora - free internet radio based on artists you type in

Evernote is a must have
USHUD is another one I like

Facebook
ESPN Sports Center - set up notifications for all your favorite teams. This is one of the best apps.
CNN - Set up notifications. You will no immediately on all world news.
Weather Channel is a very good weather app. However, I have about 5 weather apps and my favorite is Weather Bug Elite!. However, this costs $1. I typically never purchase apps for money.
Set up Home Page Bookmarks to quickly access bigger pockets, Craigslist, etc etc etc. Any website you love
Pandora Radio ---THIS may be even better. As runner and weightlifter this is GOD for working out. However, you may use up your data. I am still grandfathered in on unlimited data:)
Loan Calculator - for when you need to determine cash flow on a rental to the penny :)
Wallpapers High Def - This will make your iphone stand out with insanely cool backgrounds!
Redbox - to see what cheap movies are available and reserve them.
Flixter - to see how good the movie is before renting it for $1.50.

Andrew, why won't you buy apps when most are 99 cents? I never stop being amazed at the value of many of these apps as someone who has had to spend $hundreds and $thousands for business apps in the past. The new app economy is fantastic.

Something I did not want to get in the habit of. Surely, if something is truly amazing I would consider purchasing it. I have actually never paid for an app :) I transferred weather bug elite, tiger woods golf, some racing game etc from my brother's iPhone (for some reason apple allows this?? I was surprised). Also, I have found that the great apps, at least that i use, are typically free anyway. You can always find a free app to get the job done which is one thing that is also amazing.

Jon, I know many people wouldn't feel comfortable with my unsecured iPhone habit. But I value convenience over security in this case. If someone is going to steal my iPhone out of my pocket, they could also steal my wallet, and I'd be more concerned with losing that than my iPhone.

Thanks for bringing attention to the fact that people who choose to secure their iPhone 4S need to also set Siri to "off" when the phone is locked.

We're wandering off topic, but security vs. convenience is always a trade off. It would certainly be more convenient to not have locks on cars or houses and to just be able to walk up to an atm and ask for money with no card or pin. When a cell phone was just a phone, the risk was pretty low. But now that you can actually spend money, send texts, send e-mails, etc, the risk is much higher.

Think about a couple of scenarios that could occur when a bad actor finds or steals your phone. They can buy apps from the app store. Sure it requires your apple password, but they have your e-mail, so its trivial to reset it and lock you out of your own account. Have any banking apps? Same applies. They can reset your bank account password, log in, either from the web or from the iPhone app, set up a new payee in your online bill pay and send themselves a check for your account balance.

Now, can you unwind those things? Probably. But is that an inconvenience?

Back on the apps. I'm a bit surprised at Apple's allowing apps on one device to be transferred to another when using the same iTunes for synching them, but that does seem to be their policy. That allow buying Pages, Numbers, and Keynote once and using them on multiple devices. $30 for a pretty powerful office suite on as many devices as you want is a good deal, I think.

I've tried several note taking appps, including evernote, notes plus, and penultimate and have found pages to generally be more useful.

Downloaded RedBox last night. I've been considering dropping NetFlix in favor of redbox. Still not there thanks to the variety on NetFlix, but the RedBox app is very well done.

Photobucket has a decent app, if you use that to store photos.

I did just test and found out my iPad bluetooth keyboard works with the 4S. I guess I already knew it would. One of those foldable keyboards with the iPhone would make for a highly portable "PC". Well, and if you're as old as me, some strong glasses.

I'd really like a good drawing app like Visio or Omni Graffle. I know Omni Graffle is available for iPad, but its $50 and that's too much. Anyone know of a decent drawing (not hand drawing, which some of those note apps do) app?

On the silly end, I have Enjoy Suduko, WinPoker (a video poker training program), and recently found Nyan Cat lost in space which is a totally stupid but fun time waster.

I am surprised that no one has mentioned a couple of my favorites.

Quickoffice is great for opening and being able to modify, excel, word and powerpoint documents

10Bii financial calculator works better than the real calculator it emulates. Not only can you figure out loan payments but see what different interest rates and terms do to your bottom line. If your are buying notes you can't be without it. One of the best features is the easy mode. You don't even need to know how to use a calculator. You pick from several questions and fill in the information requested and you have your answer. There are other fin calc out there, but the one by INaDay dev is the best.

And lastly if you have as many login id's and passwords as I do, 1passwordpro stores your passwords in a vault that only takes one password to get into, but it is secure if you lose your phone or ipad.

Many great iPhone apps have been mentioned already, but I'll add the following:

Income Property Evaluator (IPV) - Quick calculator for income properties.

Rent.com App, for finding comprable rents in a given area.

Mortgage App for calculating on the run.

I just got my new phone, so this info is very helpful. Thanks for the tips.

Just found this iphone&iPad app. " sign and send" . Email attachments that you need to sign ,you can do it from there.

My favorites are:

Trulia

Evernote

Yelp

And of course the fan favorite, Angry Birds, lol

UrbanSpoon

Dropbox without a doubt the best.
Redfin
Pandora

The rest are really for personal preference.

Nice Thread! I learnned a lot. So many apps that I had no knowledge about... About Siri - even if the iphone 4s is locked, Siri will respond. Whooooa!!! I just changed the settings so Siri does not respond when the phone is locked!!

Craigslist Notification this app allows you to be notified when a new home (or anything else) is posted to craigslist. You'll be the first to contact someone when they have something for sale. I have the app on my Droid but I would assume that Apple has something similar.