They're so popular, in fact, Apple believes it will hit one billion downloads by the end of the week and with 30 million iPhones and iPod Touches sold so far, that equals roughly 33 application downloads per unit costing anywhere from 49p to £4.99. With thousands of apps to choose from, it can be a bit daunting getting started and finding the best ones, so Campaign has asked industry figures to choose their top five.
IAN PEARMAN, MANAGING DIRECTOR, ABBOTT MEAD VICKERS BBDO
FakeCall: You're in a meeting so dull, you've forgotten the name of your own mother - a couple of clicks on FakeCall and you have the perfect escape route.
Pedometer: The best way to ensure you limit your physical exertion to a minimum. If they had fitted an alarm that sounds if you exceed 100 steps a day, it would be perfect.
Evernote: A note-taking application with nifty software that makes all the clips searchable - so if you see something you want to remember later you can just cut it or take a photo, Evernote it, and then type a keyword to find it again one day. A scrapbook for life.
BubbleWrap: The distracting power of this app for a three-year-old is ten times greater than an hour of In The Night Garden. Makes for calmer car journeys.
iPity: The key to developing a managerial style based on Mr T's art of "jibba jabba".
STEVE ALDRIDGE, FOUNDER, PARTNERS ANDREWS ALDRIDGE
QuickVoice: The dictaphone I used in writing this. Not that I'm Richard Nixon, but taping the odd meeting can be really helpful. And, more realistically, if you've got a mind like a sieve it's great for quick reminders.
Remote: This lets you control your music wirelessly from your iTunes computer to any room in the house.
Polarize: This creates pictures that look like Polaroids - not just the white plastic border effect but the pictures have more contrast and are richer.
iHandy Spirit Level: I'm obsessive about things being straight. I've yet to lay my iPhone over a layout, although I'd be interested in the reaction, but no picture frame is safe.
FakeCall: You can set your phone to call you at any time. And you can set the name of that important caller to spring you out of those never-ending meetings! Is that my phone now? I've got to take this, it's Peter Scott again.
GAVIN GORDON-ROGERS, EXECUTIVE CREATIVE DIRECTOR, AGENCY REPUBLIC
Tweetie: If you tweet, there are a multitude of apps begging for your favour. But this one, as ordained by His Royal Twitliness Stephen Fry, is the best. Easy on the eye, with all the functionality you could want.
QuadCamera: A tweakable camera app that turns your dull and ordinary life into the stylised, vivid world of a professional photographer. Very easy to use and slightly cheaper than Nick Knight.
Dr. Awesome, Microsurgeon: Highly addictive game made all the more personally relevant by the genius way in which it uses your own contacts as the list of "patients" awaiting surgery. This leads to interesting dilemmas. Must save mum. Next up, Jane McNeill (the managing director at Agency Republic). Well, let's see how this profitability meeting goes first ...
Tumblr: www.tumblr.com provides functionality to write a "tumblelog" - a stream of consciousness, uncategorised blog about stuff you're interested in. I've only recently started one but they're at 96,539,730 posts as of writing.
Google Maps: This one comes pre-installed, and it's the most amazing and useful mobile application ever created. "Street View" adds extra wow factor ("There's my car!") but it's the live GPS tracking that brings it to life. Seminal and simply indispensable.
JON INGALL, FOUNDING PARTNER, ARCHIBALD INGALL STRETTON
eWallet: With a mind like a sieve and hundreds of passwords to remember, eWallet - a sort of secure mobile safe - means I can keep all my passwords and pieces of personal information in my pocket. It also holds life-saving information such as my girlfriend's shoe size. It's great as long as I remember its password.
Sky+: No need to miss those Champions League goals anymore if a meeting overruns. I can now set my Sky+ box to record the match from the comfort of the boardroom. Genius!
National Rail: As a commuter working in a job that finishes at any time between 6pm and whenever, knowing when the next train leaves can be useful. I used to get this info free via a brilliant little app from Kizoom. Those nasty people at National Rail seem to have closed Kizoom down just so they can charge £4.99 for exactly the same information. It's a great app, but I resent paying for it. Every time I open it up, it reminds me just how much I hate train companies.
Urbanspoon: Once you've found out that you've just missed the train, you may as well go and find something to eat. Urbanspoon suggests restaurants in the local area based on type of food and price. It's fun to use, great for finding new restaurants to try, and has direct links to reviews and contact information.
WorldView: With WorldView on my iPhone, I can be instantly transported to sunnier climes such as Monaco, Portofino and even The Maldives - and take a look at what I could be doing. It works even better when you're actually there. What better tonic than lying on a beach in the sunshine with a cold beer watching the drizzle fall in London.
SARAH GOLD, MANAGING DIRECTOR, CHI & PARTNERS
Tweetie: It's probably unfashionable to write this, but I'm personally a little bit over Twitter. However, when you have a colourful online social networking butter brand to manage, this was a must-have on the iPhone. Now I can feed in tweets to Maud, our twittering Anchor cow, in between meetings.
Shazam: This was a great text message service but, in my view, is an even better app as it can sit alongside my iTunes and Last.FM. As soon as Shazam tells me what a song is, the others are there to help me buy or listen to it. A brilliant example of applications working together.
Last.FM: I'm afraid I have joined the sad group of Spotify evangelists, and this app basically gives me Spotify on the move. The more I listen, the more it understands my music taste. I never knew there were so many Take That- alikes out there.
Wikipanion: Who doesn't need this? Except Gail Trimble. But being a student, she probably hasn't got an iPhone. Unlucky.
AroundMe: I don't use this one much but feel like I should have it on there as it's a clever little thing. It makes me feel safe in the knowledge that wherever I roam, I can always locate a nice cup of green tea or a restaurant serving perfectly cooked kippers.