Calling phones in the United States is now completely free for all uniformed military personnel with a valid United States Military (.mil) address. This means that troops stationed around the world can now call the United States at no cost, right from Gmail.
Step 1: Add your .mil address to your Google Account:
Step 2: Click the 'Call phone' link in your chat roster and use the dialpad to make calls. You may be prompted to install the Voice & Video Chat plugin.
Similarly to free calling within the U.S., free calling to the U.S. for service members will be available for at least the rest of 2011. Calling to other destinations starts at as little as $.02/minute, and calling from Gmail is not available in all locations.