"The world's largest collaborative phone directory to find people from all over the world through name and phone number lookup. Get the app for free to your Android, iPhone, Windows Phone, Blackberry and Nokia Symbian phone."
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 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.