Note: This review addresses version 4.0 of the software.
Here's the simplest way to save money on your phone bill: Use Skype. It lets you make Internet-based VoIP (voice over Internet protocol) phone calls for free to anyone in the world who also uses Skype on their PC, and make inexpensive calls from your PC to landlines and cell phones worldwide. It's also an instant messenger as well.
If you've heard of Skype, but worried that it's hard to set up, worry not. It's exceptionally simple to use. It will automatically recognize your headset, microphone, and speakers, so you don't need to worry about configuration. To call another Skype user, enter a user name, and you're ready to go. You can also save a list of users, so calling them back is simple. To call landlines and cell phones, you'll need to set up an account and buy credit. Then, whenever you make a call, that credit is used.
Skype does more than phone calls. It also lets you video chat and text chat as well, and send SMS messages. This newest version of Skype also features nifty integration with Firefox--you can call any phone number you see on a Web site with one click.
Note: This link takes you to the vendor's site, where you must register to download the software.