SIPDroid free phone with Android :

Sipdroid client is a SIP / VOIP
for Android to make and receive telephone calls over
the Internet using, for example, your SIP account
Free.
Some operators block VoIP software on 3G. We must
therefore pass through WiFi. SIPDroid is an
application that you find on the market Android, or
on the website SIPDroid.
To run the software you need to register with a SIP
provider like pbxes.org (free).
If you have a freebox, it will go on your account
and under phone, activate the SIP.
To configure your account pbxes instructions should
be followed (in French) SIPDroid wiki site.
The new version of SIPDroid allows video calls.
Finally, remember that you can use the software to
find WiFi Freebox Free WiFi hotspots and make calls
and with Sipdroid.
Here is the procedure:
To activate your Free WiFi at home, here's how:
1) Place front of your Freebox
2) Put yourself in WiFi. Launch Internet and enter
the address and watch your http://wifi.free.fr
Freebox, it will display a four digit code that will
then enter on the form
3) Confirm and enter a password of your choice