After rolling out the unified Hangouts, Google took out the ability to make free calls in Gmail. It’s a good thing they’ve been listening and brought the feature back. They even improved it further by making calls to the US and Canada free for countries where Hangouts calling is available.
Other new features their adding to this “future of Google Voice” include being able to add multiple phone numbers and video participants to the same call as well as playing sound effects using the Google Effects app. These new additions are said to be coming out in the next couple of days.
Source: Gmail Blog