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.
ClearSea - mobile video calls Professional Videoconferencing on 3G/4G/WiFi connecting to other ClearSea PC/Mac/mobile and any standard H.323/SIP device (Tandberg[tm],etc)
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
IMSDroid High Quality Video SIP/IMS client for Android
Yelo : Cheap Calls Worldwide Use the Yelo App to make cheap calls to anyone, anywhere in the world on their normal mobile or fixed landline numbers. No more shock phone bills!
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)
Voip One Click Voip One Click is an Android app which allows users to make free encrypted VoIP calls
MO-Call Mobile VoIP on Android MO-Call offers savings on international calls made from your mobile device. Use the MO-Call app to make cheap calls through Callback calls to avoid roaming rates wherever you are
Ventriloid Ventriloid is an open source Ventrilo 3.x client with a familiar UI. Ventriloid is based on the Ventrilo library for Linux created by the developers of Mangler