Okay, here's the deal, there's another thread (http://www.ipodtouchfans.com/forums/showthread.php?t=19934), I know, and thanks everyone for posting in that thread. This is GREAT, please continue to do so. However, it's hard and annoying to go through a whole thread to find SIP Provider, their Registrar address for app, and their pricing; so what I'm gonna do is compile them here as they pop up, and sticky this thread, so its easily accessible by all. Please note that by listing them, I'm NOT endorsing them or recommending you to use them. I do not get paid from any of them, and do not work for any of them. Keep in mind, hundreds of thousands of iPod Touch / iPhone owners will be trying to use them over the next while, so they will be very busy. It is more than likely that some of them will actually die because of the excess amount of publicity they've received because iPod Touch / iPhone now supports VoIP. If their service goes down, don't ask me when they will be back. If you see me missing a few, let me know via PM, and I'll update it as soon as I get back around to it. So with that said, here we go!

VoIP Raider
Site: http://www.voipraider.com
Registrar: sip.voipraider.com
Pricing: http://www.voipraider.com/en/rates.html

Voip Buster
Site: http://www.voipbuster.com
Registrar: sip.voipbuster.com
Pricing: http://www.voipbuster.com/en/rates.html

Blueface
Site: http://www.blueface.ie
Registrar: sip.blueface.ie
Pricing: http://www.blueface.ie/rates/rates.aspx

TerraSip
Site: http://www.terrasip.com
Registrar: terrasip.net (port: 5060 if needed)
Pricing: http://www.terrasip.com/index.php?seite=tarife4&language=en&t_country=us

Free Call
Site: http://www.freecall.com
Registrar: sip.voiparound.com
Pricing: http://www.freecall.com/en/rates.html

Voipcheap
Site: http://www.voipcheap.com
Registrar: sip.VoipCheap.com
Pricing: http://www.voipcheap.com/en/rates.html

NetVOIP
Site: http://netvoip.ch/index.php
Registrar: <unknown; pending reply> (please try: sip.netvoip.ch if you have an account, and let me know via PM).
Pricing: http://netvoip.ch/rates *Note: pricing in CHF, not USD

VYKE
Site: https://www.vyke.com/merchantsite/main.c?Distributor=MASKINA&Locale=7
Registrar: sip.vyke.com
Pricing: https://www.vyke.com/merchantsite/rates.c?Distributor=MASKINA

Gizmo Project / SIP Phone*
Site: http://www.gizmoproject.com/index.php
Registrar: proxy01.sipphone.com
Pricing: http://www.gizmoproject.com/call-out-rates.php

*Note: Gizmo Project does not currently work with 1.1, there is some codec priority issue (I think). I spent some time with devvies in the afternoon today, chatting about it. It is being aimed to have it fixed by the next version (rumours have it that it will come in next 10 or so days).