Google has introduced voice and video chat from gmail. All yo need is a plugin which can be installed from within Gmail.
You can view the videos in the small fly-out panel or pop-em out to a large PIP view. You can even blow them up to full screen and have a smooth chatting experience at the same time.
Below is a video tutorial highlighting some of the features of this new service along with instructions on how to use them.
Voice and Video Plugin Direct Download