EDIT - This article is outdated, and the information no longer works. For free incoming/outgoing calls with google voice check THIS newer article.
[EDIT: Gizmo is being discontinued by Google.]
I have seen many outdated articles related how to get GV and Gizmo to work together so that you can have not only free incoming calls, but also free outgoing calls.
Since Google Voice has disallowed incoming SIP connections, and since Gizmo no longer has this as an option, I will discuss the way that I have been able to make free outgoing calls from my Gizmo account using Google Voice.
My first test was to just use click to call to call into my Gizmo number, but for some reason when I answered the GV call from Gizmo the line only rang once and then I was faced with silence. Knowing that my GV number works, and that I am able to call into it with no problems with other phones, I figured that somewhere the GV number realizes that the CID is calling itself. Click to call displays your Google Voice number, not your Gizmo number as the CID, So I assumed that this is where the problem lied.
So with the above informatiion to guide me into a way to make free calls I decided to try one of the other Google Voice numbers that I have access to, in conjunction with my Google Voice number,
Here is the soloution - you will need 1 Gizmo account, and 2 Google Voice accounts.Gizmo is currently in closed beta so if you do not have a Gizmo account then you will need to find a different soloution (such as a VoIP buster account with an ipkall DID)
Gizmo account - self explanitory
Google Voice account #1 - this is the account that you will link with your Gizmo account (or other VoIP provider with a US DID)
Google Voice account #2 - this will be the number that you call from GV account 1, and will appear on your CID for your placed calls.
If you already have a GV account that you use that is connected with your phones, then you will want to use this account as the GV account #2
with GV account #1 (a new account if you have one existing GV number that you use to receive calls) link this with your Gizmo account, and set up an address book contact with your GV #2 account phone number.
unfortunately you can not add a GV number as a forwarding phone with your GV #2 account, so you will have to enter * and your pin every time you make a call, but I guess that is a small price that you pay for unlimited FREE calls to US and CAN.