I've come across this wonderful program called Firefly Softphone. It's available to download for free from http://www.virbiage.com/firefly/

Basically, if a friend or relative has this installed on their PC, whether they be on the other side of the world or just around the corner, you can talk to them for free. Obviously you need a sound card, speakers and a microphone, and I think that the clarity is equal to a normal landline telephone.

With regard to the speaker/microphone part........ it's better to use a headset than a separate microphone and speakers, then the other person won't hear themselves a split-second later through their PC.

It is easy to set up, simple to register a number (has to be between 80000000 and 89999999) give a few details and they email you your password. 

Adding a Contact is done by simply right-clicking on the Firefly screen,  selecting Add Contact and filling in the details of your friend. Choose any wav file you want to be your incoming call audible notification. Choose a nice mp3 for callers to listen to if you are on a call or away from your computer. There's Voicemail so that callers can leave you a voice message and you can do text messages too. All in all, it is a good program and easy to use. It could also help reduce phone bills, especially if you have someone living in Oz or America. Try it. It's free, and you can always uninstall it if you don't like it.

Happy Chatting.