Google is shaping Gmail into the ultimate communications hub. Today, the company announced that United States users will be able to make and receive calls within Gmail, providing they install the company's voice and video plug-in.

Users could already call and video chat with other Gmail users, but the new features allow them to call landlines and cellphones. Google says that calls to phones within the U.S. and Canada will be free for at least the rest of the year, and calls to many other countries will cost 2 cents a minute.

Google writes:

We've been testing this feature internally and have found it to be useful in a lot of situations, ranging from making a quick call to a restaurant to placing a call when you're in an area with bad reception.

Google previously made a foray in Gmail-to-phone communication with an experimental feature that allowed users to send text messages to phones. It was a smooth, impressive step toward blurring the lines between the different forms of communication that people use on a daily basis. However, abuse of the system (including an iPhone app that piggybacked on it in order to provide users with free text messages) pushed Google to limit its functionality.

By adding the ability to call phones, Google is pushing to set Gmail apart from other webmail services, and it probably means other communications systems will be centralized within that interface.