First, there was Gmail, a free email service. Then there was Google Voice, a free phone calling and voice mail service. Next came Google voice chat. And as of last August, they're all combined in the new Gmail-based phone calling service. Gmail users with the voice and video plug-in can call any phone right from their browser, through the Gmail chat function. Calls to the U.S. and Canada are free for now, and calls to other countries are about the cheapest around. This surely makes for some awkward moments when Google meets with its mobile carrier partners to discuss Android, companies that can expect to see their voice revenue decline if online telephony continues to appeal to users.