can share you one good Free Voip server… the fonosip…
I’ve been using it now.. I can apply it to any SIP phones, it doesn’t require your phone to be Skype ready or any other provider ready.. all you need is make an account at Fonosip.com then make your own extension number. Then after you have succesfully registered, configure any of your IP/SIP phones using server, username and password from Fonosip.. I suggest you make many accounts, so that you can make your own VoIP Network, without availing any IP PBX server equipment.. :-)…