Skype

Skype is a phone call via your computer. Very easy to set up - you'll need a computer, internet access and a microphone. If your computer has a built in video camera or if all parties have a webcam - you can video chat as well.

Go to skype.com to download their free software.

http://www.skype.com/

Here is a tutorial showing you step by step how to get started:

http://www.roch.edu/dept/et/articulate/skype/player.html