- Rebtel: Rebtel offers a similar app like Viber. The compnay is based in Stockholm, Sweden, founded in 2006 and currently the second largest after Skype. The interface is very similar to iphone native dialer (on ios) and is better than Viber as it allows you to dial mobile and landline numbers at very low cost. Rebtel to Rebtel calls are free.
- WhatsApp: http://www.whatsapp.com/
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, Windows Phone 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.