Google Voice:
Well this is a pretty impressive app which allows the person for making international free calls. Well this app presents its exclusiveness to the citizens of U.S. and Canada to make free calls within the countries and for people around the world it costs very few.
Vonage:
This particular app is a bit different from Google Voice and is certainly the premium Internet calling service in U.S.A and Canada. To avail this facility there is a monthly subscription fee which involves a fixed rate for international calls.
Rebetel:
This is another Android app in which the user can make free/cheap calls which converts longer distance phone calls into local phone numbers, but infact the user has to pay according to the company’s specific contract.
Truphone:
This is a pretty popular app in this field which lets the user to make free calls to another user having Truphone app and in terms of worldwide the charges are of lesser cost.
Skype:
This is a very famous application which allows the user to make interesting calls; especially video calls over the network. The calls are free among the Skype users and costs a very little charge over mobiles and landline networks.
To download any of the app, just search for them in the Android market on your mobile.