Android Market

Sipdroid is an open-source SIP client for Android. This version supports VoIP over your Wireless LAN only (no voice over mobile data).

BigTinCan is a virtual calling card that allows you to make calls using your standard cell phone service at VoIP like rates. BigTinCan uses a callback system to connect your phone and number you are calling over the cell phone network, and you get a range of features including call recording, flexible caller ID and more.

Vopium the VOIP calling service similar to Skype is now penetrating into Andriod market and working on Vopium Andriod cleint. However, the rates are quite competitive to say the least. It is powered by WIFI and mobile VOIP technology and can help you save up to 90% on phone calls and cheap SMS. Vopium has recently added their application on Apple app store and it’s also available on Blackberry app store. Vopium offers affordable internationals calls to mobile and landlines and helps slash phone bills significantly. At the moment the service is available in Europe, America and Australia and free 30 min calls and 30 sms at signup. More details on packages can be found at http://vopium.com/products.