Here are links to the various guides I have done.
A few words on GTalk Trunks not quite a guide, but those who have read the others can put 2+2 together and improve your setup with what I mention…at least until I get time to make a new guide
Updated Sipdroid/G. Voice Guide (from XDA) March 12, 2o10 This guide uses SipSorcery to perform callback. It does not require the GV app
Original Sipdroid/GV Guide (from XDA) very old but still useful. This is the original guide that uses GV app for callback
XDA Thread the comments here may help some who are having trouble.
These were all written a while back. The original one was done when their was only 1 android phone. There are lots of alternatives to SIPdroid now, and loads of handsets to run the apps on. Though they are slightly dated, these guides cover the basics of setting up a working configuration.
With that being said. Please understand I am not capable of testing on every device or every carrier. If you have followed the guides, and still need help, visit the forum for your device @ XDA. They have a wealth of information on everything Android related, and are quite helpful. You will get your question answered a lot sooner over there.