Google Voice- Place calls and send text messages showing your Google number. Listen to voicemail and read transcripts. Currently only available in the US. NEW: Search your voicemail transcripts and text messages.
Skype (Android) With the Skype app, you can make free Skype-to-Skype calls, and send and receive IMs for free, one-to-one or with a group
GroupMe Start a group, add your friends, and we’ll give you a free phone number for it. GroupMe is the easiest way to start conversations and keep in touch with your real life network. It's totally free, and it works on every phone
Zadarma Thank's to the new tariff "Free" every user of Zadarma can call to 25 countries of the world absolutely for free
G1 Central (Android) G1 Central is an application for Android-powered phones which allows you to place calls to any number from your GrandCentral number
Cheap Calls - XonXar App Xonxar finds the cheapest rates amongst many VOIP providers and allows you to use them without subscribing with those
Linphone Video Linphone is an open source internet SIP phone or Voice Over IP phone (VoIP) WIFI/3G, with video calls support for ARMv7 phones. Main features: -Audio with the following codecs: speex (narrow band and wideband), iLBC, G711, GSM -Video with mpeg4 and H264 codecs (ARMv7 only)