Skype - Skype-to-Skype calls over 3G or WiFi ? Call phones abroad at great Skype rates ? Instant message one or many friends at the same time - Data plan or WiFi connection required (calling in U.S - WiFi only) - Some handsets (e
fring gives you FREE Video Calls, voice calls & chat to friends over 3G and WiFi (Video calls only on capable devices).
Communicate with friends in the fring network and other supported services: MSN Messenger, GTalk, Twitter, SIP, Yahoo!, AIM & ICQ
Turn your Android into an IP Phone with Cisco Jabber for Android. IMPORTANT: Cisco Jabber for Android requires an account with your company's Cisco Unified Communications ManagerTM and will not work without it
Mobile VOIP - Cheap calls using MobileVOIP over 3G or Wifi!
Call for free: The MobileVOIP dialer lets you make cheap calls to national or international destinations
MobileVOIP - With MobileVoip you can make free* voip calls from your mobile phone. Make calls to any country you desire at the cheapest rates. MobileVoip is currently supported on iPhones, Android phones and Symbian phones. Simply download the free MobileVoip app from one uour APP market and register with one of the supported Voip brands
CSipSimple - This project will allow native sip for Android devices.
It relies on the pjsip sip stack and use the pjsip-jni project.
The use of this native library will ensure a better speed, call quality and less battery consumption than equivalent pure java projects
Adore SIP Client (Android) - AdoreSoftphone has come up with " SIP Client for Android (VoIP)" for Android based Mobile phones. Android VoIP Mobile dialer lets the callers make VoIP calls through their standard Mobile phones. The Android Softphone is meant for service providers who can use this Softphone and get it integrated with their existing SIP servers
Skuku - Make and receive calls and SMS when abroad using your SIM card and cellular identity without roaming charges.
Notes:
Cannot be used for emergency calls.
Requires a Wi-Fi connection.
Using Skuku Roaming service requires root access