There is an F'ring thread on the front of the site.
Download the program and go. It connects you through your SKYPE account or other accounts (that I don't use or recognize) which allow voip. F'ring is f'ree, but most Skype services cost a little bit if you are calling non-computers.
Overall Skype is excellent if you have a way to use an iPT and have wifi all over. In that case you only pay about $25 for a year of unlimited calls in North America, maybe the world.