An app that was once only available on the Apple iPhone is now available on the Google Android based phones and it's called Viber. Viber allows you to call and SMS your friends without using any of your minutes in your calling plan from your phone provider. Viber utilizes 3G or WiFi to makes calls over the Internet. Best of all, no registration is required and you use your existing phone number on your mobile device. Viber already has over 12 million active users using their service and trafficking over one billion minutes of calls per quarter.