Straight from the Google Blog:

"Last week, I was trying to buy blue lightbulbs for a party at my house, and I ended up calling ten different stores before I found one that carried them. Now with the new calling feature on Google Maps, I can do this quickly and easily, and never have to lift a finger to dial.

Here's how it works: Search for a business, like a hardware store, on Google Maps, and click the 'call' link next to its phone number [insert link of live example]. Then, enter your phone number and click 'Connect For Free.' Google calls your phone number and automatically connects you to the hardware store.

There are two things that I really like about this. The business's phone number is automatically stored in your caller ID so you can easily call back in the future. And by checking the box to save your phone number, you can make future calls from Google Maps with just two mouse clicks (after you pick up your phone, of course).

We're offering the 'call' link as a free service to all businesses. These aren't ads and don't influence the ranking of businesses in the search results. We foot the bill for calls (local and long distance), but airtime fees or other mobile fees will still apply if you use a mobile phone number. Currently, the calling feature works if you live in the U.S. and are looking for a business located in the U.S.

Learn more about this, and also our privacy policy."

http://googleblog.blogspot.com/2006/11/click-to-call-in-google-maps.html

Notice the: "[insert link of live example]"!

Update: I have just done a few searches all the businesses have the call button. I don't have a US phone number so I can't actually test it – it refuses my international (UK mobile) number. If anyone with a US phone would try it I would be interested to see how well it works.

Worked perfectly. I connected my workplace to my cell phone.

It called my cell phone, and as soon as I answered I heard it ringing the business. Nice feature.

What about prank calls with this though? Wouldn't it be rather simple to say look up a Hair Restoration Clinic and enter your balding buddies phone number on there?

<<What about prank calls with this though? >>

heh.. i just tried it on my coworker in the next office. Worked like a charm. Connected him up to a child daycare business. (chuckle)

lol..
sounds like a great prank.. he he.. :)

but how Google can pay those pranks..? i think they should embed ads on each call made..

dont you think guys?
kinda like this way:
Ring , ring.
(accept call)
Hello, this call was brought to you by .... you will be accepting it in 3 seconds, thank you.
(a regular talk with the representative)

<<# What if someone enters my phone number instead of theirs as a prank call?

Google takes fraud and spamming very seriously. We use technical methods to prevent future prank calls from the same user within a reasonable period of time. You won't be charged for any such calls. Please contact adwords-supportgoogle.com if you believe someone is entering your phone number without your permission or knowledge. >>

Unfortunately, the number and address they have for my company is out of date by years! and to change it you have to either verify your number or address... Guess I'm outta luck

has anyone tried to call into a fax# ?? a Prank call to a fax# , could also be a type of DoS attack ..

Garrett Rogers wrote about that some days ago :
http://blogs.zdnet.com/Google/?p=389

And I like this article from Valleywag :
http://www.valleywag.com/tech/latest-wizardry/prank-calls-from-google-maps-215193.php

The little devilish me punched in some (phone) numbers... :) Getting them to talk to a real person is better than doing it on Skype. :D (Free phone calls to the US and Canada, with a crazy phone number.)

will google use it's need adsense audio to give you a short add down the phone before you are connected in the future?

Is it me, or is this feature gone at the moment?

I see business phone numbers, but the call link isn't there.

youre right Dave..
its not there.. :/

The Click-to-call feature is missing for the same results for which it was present Saturday night...