Sent to you by tony via Google Reader:
Google was coy about reports earlier today that users were discovering a "call phone" button in their Gmail accounts, but the company has just confirmed that over the next few days, they will be rolling the ability to call people directly on their phones is coming to Gmail, and that until at least the end of this year, the service will be free for calls to the U.S. and Canada.
Calls to other countries will be priced in accordance with this rate table. If you don't currently have money in a Google account, you'll need to add it by clicking on your credit balance and adding credit using Google Checkout.
If you're interested in trying out the service, you'll first need to install Google's 22 MB voice and video package (available at the link if you don't already have it); from there, the phone icon will appear at the top of your chat list if it's enabled for you. Click on that and you'll be taken to a panel where you can punch in phone numbers. If you're interested in receiving calls in Gmail, the setup is a little more involved: You'll have to set up a Google Voice account, make at least one outbound call from Gmail, and follow these instructions.
One final random tidbit: If you're Canadian, you can use the new service by changing your Gmail settings to English – US. (h/t Peter Norwak.)
Below, Google's demo video: