ActionVoip 

ActionVoip is a free piece of software aimed at voice communication, a voice over IP utility. It permits for calls to be made from computers to regular phones, with no charge being applied for certain destinations, while others can be called at low rates. Both mobile and fixed phones can be called, SMS messages can also be sent and computer to computer calls can be made.

For starters, you will have to create and activate a user account and perform a bandwidth test. Audio devices will then be configured. The user interface is simple to use. There are six different tabs in the work area. The "info" tab will show you your account credit, contacts will be listed in another tab, a dialpad is available for dialing phone numbers. Three other tabs are built in: "Phone2Phone", "SMS" and "History". When dialing phone numbers, local ones included, the following rule should be applied: dial 00, countrycode, areacode, subscriber's number, in this order. A nice feature is that contacts can be imported from Windows Live Messenger, from Skype and Outlook. However, it would be nice if Yahoo Messenger contacts could also be imported.

All in all, ActionVoip is a good tool for making computer-to-phone or computer-to-computer calls. The list of call fees is available at http://www.actionvoip.com and pc-to-pc calls are free of charge.