Calling! In Gmail!. It's been rumoured for a little bit, but now it's here. Merged. You can make phone calls from Gmail (without going to your GV page).
How's it going to work? You can make calls in Gmail, and then talk directly to your computer. Google says the call quality is "really good", even just using the standard mic and speaker in the laptop you have. They claim they have really good echo cancellation - the same one they use on the video/voice chat in Gmail.