I see lots of phone cards floating around and I hear they use voice over Ip. I am interested in finding out the kind of equipment they and how how everything works.

I don't think this is the right forum to ask this. :)

And while I do know how it generally works, I can tell you it's all quite complicated, and you can't just start up a server and sell cards -- you actually have to make deals with phone companies and so on. So in other words, you need $$$ to start. :D