SIP Service Providers - InPhonex

InPhonex offers a free SIP phone number service. They make their money selling a PSTN gateway service (to make real phone calls) and hardware (SIP routers) etc.

InPhonex can also provide a 'real' phone number for residents in USA, Canada, and the United Kingdom.

Sign Up Here: http://www.inphonex.com/reg/newuser.php

SIP Configuration Settings:

SIP Number/Username: [Your Inphonex Number]
Password: [Your Inphonex Password]
SIP Proxy Server: sip.inphonex.com