iPhone must have applications

1.Viber - an iPhone application (Android and Blackberry versions coming soon!) that lets you make free phone calls to other iPhone users that have Viber installed.

When you use Viber, your phone calls to any other Viber user are free, and the sound quality is much better than a regular call. You can call any Viber user, anywhere in the world, for free.

2.WhatsApp- a smartphone messaging app which allows you to exchange messages with your friends and contacts without having to pay for SMS. WhatsApp Messenger is cross platform and available for iPhone, BlackBerry, Android and Nokia (beta) and yes, those phones can all message each other! To send and receive messages, WhatsApp utilizes your existing smartphone internet data plan: 3G/EDGE (or Wi-Fi when available)

In addition to messaging, iPhone, Android and BlackBerry WhatsApp Messenger users can send each other unlimited images, video and audio media messages.

3.Awesome Note-an innovative note taking application and to-do manager that allow you to combine notes with to-do flexibility.
Awesome Note enables you to customize its look with themes the way you want it to be displayed with different folder icons, colors, fonts and paper backgrounds.

From easy-to-use regular notes to notes with multiple photo attachments, To-Do Notes to organize your day, Post-It style Quick Memo to quickly jot down your thoughts, sending notes with photo attachments as email, and synchronization with Google Docs / Evernote, Awesome Note provides some powerful features.

Jot down your ideas, thoughts and memos, and create daily diary, travel diary, email box, checklist, shopping list, to-do list, scheduler and anything else you want and sort them into custom categories with Awesome Note.

4.Dictionary -The free Dictionary.com app delivers world-class reference content from Dictionary.com and Thesaurus.com including nearly 1,000,000 words and definitions and 90,000 synonyms and antonyms. No Internet connection is needed. The app also features audio pronunciations, similarly spelled words and Dictionary.com's popular Word of the Day that is enjoyed by millions of people.

5.iExpenselt - a full-featured expense tracker app for your iPhone. Mind you, while the app's interface may look simple, it is however a very powerful app that will enable you to do so many things. Of course, the ultimate goal is for you to better manage your budget by tracking your daily expenses for food, transportation, and practically all your personal and business transactions.