IP Telephone?

Hi everyone
Well here it is
I have some good-old friends halfway around the Earth and I'm really willing to talk to them, but telephone is way to expensive (for a normal length conversation), E-mail is not fun anymore, and I'm afraid they do not have time to use a webcam or any thing like that, so I thought of an IP phone.
Can I have one right at home, at my PC?
And are there any free IP Phones, so that I don't get to pay anything else but the internet bill.
And how does it work? I mean all I know about an IP phone is that it exists. Help plz
Thanx