Remember how Google lured people to Gmail by providing huge amounts of online storage? It's doing it again with phone calls.

Google today announced that Gmail users can make free long distance calls in the U.S. and Canada through a cool new feature that lets you place calls from wtihin Gmail to a mobile or landline phone.

"Call phone" is a new option in Gmail's list of contacts to chat with, on the left side of the page. You can dial with a keypad that pops up, or enter a contact's name to call them.

Calling phones from computers isn't new but Google's built a simple system and underwritten its launch with a generous batch of free calling.

From Google's announcement:

Gmail voice and video chat makes it easy to stay in touch with friends and family using your computer's microphone and speakers. But until now, this required both people to be at their computers, signed into Gmail at the same time. Given that most of us don't spend all day in front of our computers, we thought, "wouldn't it be nice if you could call people directly on their phones?"

The offer's the latest way consumers are benefiting from the ongoing battle over Web services Google, Microsoft and Yahoo. It also comes as students are heading back to school, setting up new email accounts and choosing which services they'll use to stay in touch with friends and family.

Gmail's calling is a great deal, but it also reflects the new financial realism affecting the maturing seach company.

Unlike the online storage accounts provided with Gmail, which are perpetually free and continue to expand, the free long distance calling is promised only for the next four months.

After that, Gmail customers accustomed to the service - and new Gmail users drawn by the calling - will presumably have to start paying fees.

Google's also charging from the start for international calls placed through Gmail. They have per minute fees ranging from .02 cents to $4.99. Calls to Mexico are 10 cents a minute.