WhatsApp Messenger……… is a cross-platform mobile messaging app which allows you to exchange messages without having to pay for SMS. WhatsApp Messenger is available for iPhone, BlackBerry, Android, WindowsPhone and Nokia and yes, those phones can all message each other! Because WhatsApp Messenger uses the same internet data plan that you use for email and web browsing, there is no cost to message and stay in touch with your friends.
I have been using WhatsApp for a while now, after a friend mentioned it to me, amazed I wasnt using it! It will grab your phone contacts and list them if they also use WhatsApp, allowing you to message them instantly without having to pay the cost of a SMS, Its intuitive and easy to use as any other messenger, you can very very quickly and easily swap photos and videos with your contacts. The only drawback is that it is rather hard to appear offline! or even go offline, you can block contacts, but once WhatsApp is downloaded you are always there!