The aQuantive exodus from Microsoft continues. Just yesterday, we reported that Karl Siebrecht -- the former president of aQuantive's Atlas unit -- planned to leave Microsoft to join Seattle online advertising startup AdReady. Now, we've received word that three other former aQuantive execs who held general manager titles at the software giant -- Aaron Easterly, Brian Handly and Brent Turner -- also gave notice last week. And one of those execs has already landed a new job at a Seattle online advertising company

The departures come 25 months after Microsoft acquired Seattle-based aQuantive for $6 billion, a deal that still ranks as the largest in the company's history. We've heard that some key aQuantive employees were locked into two year employment agreements, and now that the agreements have expired they are once again free to pursue other opportunities.

A Microsoft spokeswoman declined to comment on the terms of the employment agreements.

We haven't tracked down where Easterly or Handly are headed, but we have learned that Turner is going to Marchex, where he will serve as executive vice president of call products. Marchex Chief Operating Officer Peter Christothoulou said they are "psyched" to have Turner -- who he called a "hard-nosed operator" -- on board.

At Microsoft, Turner held the title of general manager of search and display media auctions. Former aQuantive chairman Nick Hanauer is on the board of Marchex, and spoke highly of Turner.

Microsoft has lost some other key employees who came over in the aQuantive deal, most notably former aQuantive CEO Brian McAndrews who announced his plans to join Seattle's Madrona Venture Group on August 13th. (That was exactly two years after the aQuantive deal closed).

It will be interesting to see what comes of the talent pool, and whether they stay at Microsoft, go on to create new companies, take positions at existing firms or leave the area. At least with the current list of departures, it looks like many are excited to dip their toes back into more entrepreneurial projects.

Microsoft issued this statement on the recent departures:

We can confirm that Aaron Easterly, Brian Handly, Karl Siebrecht and Brent Turner are leaving Microsoft to pursue other career interests. The four of them have held senior management roles within the Microsoft Advertiser and Publisher Solutions Group (APS), as well as leadership roles at aQuantive prior to the announced acquisition in 2007. Each committed to help integrate, build and foster the growth of what is now the APS platform, which services the Microsoft Advertising sales field.

The fact they’re moving on is the reality of people changing jobs and careers and each of them being an entrepreneur at heart – nearly all started a business prior to working at aQuantive. While it’s difficult to see talented people go, it’s because of their leadership and hard work that our business is structurally sound. Scott Howe and the APS leadership team is committed to driving toward our mission of being a leading digital technology and media company.

[Hat tip to Joe Tartakoff at paidContent]