Google's 2010 acquisition-spending spree has so far involved 40 companies and a total of $1.6 billion, the company revealed today.

It's been a busy year for the men and women of Google's mergers-and-acquisitions team, closing an average of 4.4 deals a month, according to Google's quarterly report filed with the U.s. Securities and Exchange Commission on Friday. The top three deals involved AdMob, at a final price of $681 million, Slide, at a final price of $179 million, and On2 Technologies, at a final price of $123 million.

But Google also completed 37 other deals by the end of September, spending a total of $626 million on those smaller deals. Google CEO Eric Schmidt wasn't kidding when he said Google was planning to open its checkbook in 2010.

This haul doesn't even include the travel software company ITA, which Google proposed acquiring for $700 million in July. That deal is expected to face a great deal of antitrust scrutiny from the U.S. government, and Google said in its filing that it doesn't expect the transaction to close until the first half of 2011.

With $33 billion in cash to close the third quarter, it's not like Google sweated the payments on any of these deals. And given the resurgence of the online-advertising market that fuels Google's profits, don't expect Google to take its foot off the gas anytime soon.