That was fast.

Longtime–well, five years, which is a dog’s age at the search giant–Google sales exec Dennis Woodside (pictured here) will become VP, Americas Operations, replacing outgoing exec Tim Armstrong, who was named chairman and CEO of Time Warner (TWX) online unit AOL last week.

Woodside, 40, will start in the next few weeks, said Google (GOOG) in an internal communication about the appointment, as Armstrong transitions from Google to AOL. It is the key advertising sales job at Google.

Armstrong has already been hard at work at AOL, in fact, leading an employee rally today at its former HQ in Dulles, Viriginia, which included former AOL execs Steve Case and Ted Leonsis.

(And he will hold a similar meeting at AOL’s New York office tomorrow, BoomTown has been told. But let’s hope he does not roll out, say, former Time Warner CEO Jerry Levin, which would be taking this old-home-week stuff too far!)

While Woodside is a well-known exec within Google, his name was not as prominent in the speculation about which internal Googler would be named by CEO Eric Schmidt to replace the well-known Armstrong.

Wrote MediaMemo’s Peter Kafka last week, for example, when the Armstrong departure was announced:

“According to a (very informal) flash poll of Googlers, ex-Googlers and Google competitors I conducted last night, the answer should be obvious: David Rosenblatt, the former Doubleclick CEO, who now runs Google’s display business.”

Woodside will also have a slightly lesser title than Armstrong, who was a corporate SVP, was president of the America Operations and was also on Google’s powerful operating committee.

But that’s part of the changes, mentioned in a long statement by even bigger sales boss Omid Kordestani, SVP, Global Sales & Business Development, to whom Woodside will report (the key graph is the last one, although the golf dig is funny):

In the five and a half years that Dennis has been at Google (that’s over half our company’s lifetime) he’s brought incredible integrity and entrepreneurialism to everything he’s done. I remember Dennis setting off from Mountain View in 2005, a year and a half after he joined, to start our direct sales operations in Eastern Europe, which he quickly transformed into a substantial part of our business. He also set up our Inside Sales Operations in Dublin – again building it from scratch. In September 2006, he became our Vice President for the UK, Ireland and Benelux where he’s helped to create a first class team as well as establish very positive relationships with our big partners on both the advertiser and agency side, including 02, Marks & Spencer, Amazon and Omnicom.

Ever since I met Dennis in 2003, I have been impressed by his combination of entrepreneurialism and operational excellence. He’s never afraid to try new things and always ready to roll up his sleeves and pitch in–whether it means moving his desk to sit with the UK DSO team to see the operations first hand, or being the customers’ advocate internally to help product and engineering better understand market trends. Outside work he loves to do triathlons–though I would only recommend training with him if you don’t mind being out-run (if you are looking to beat him, try golf).

While we are all sorry to see Tim move on, change always brings new opportunities. We believe it’s now time not just to roll-out globally the best practices from the different regional sales teams–the Americas, EMEA and Asia Pacific–but also to tailor our business strategies more closely to the different situations we face in different countries (more mature versus less mature markets).

As soon as he got his new job last week, new AOL Chairman and CEO Tim Armstrong sent out a rather hopeful email to the troops–his first communication as the latest leader of the ragtag online service.

“I’m really looking forward to seeing you and would love to hear your thoughts and suggestions,” wrote the former Google (GOOG) exec Friday (who alarmingly kind of resembles this Elvis image), “on how to make AOL and its sister properties the most powerful brands on the Internet.”

Well, one can hope!

To goose that dream, although he still does not officially start in the job until April 7, Armstrong is also addressing all the troops tomorrow at 11 am EST and has chosen to do so from, of all places, AOL’s old center of power in Dulles, Virginia.

AOL staffers I spoke to also hope most of all that Armstrong will quickly and transparently lay out plans for a spin-out of the Time Warner (TWX) online unit from the media conglomerate, where it has languished for years.

“Armstrong would not have taken the job if the plans for a spin out of AOL were not in place and it’s in everyone’s interests to signal that it’s a go right away,” said one source close to the situation. “The only catch is the poor economy, but even that should not prevent Time Warner from doing what’s right to finally fix AOL.”

And sources said Armstrong could further up the ante tomorrow and help raise the layoff-weary morale by having some former AOL execs from its glory days as the top online player in person at the event.

Several sources said one exec most likely to make an appearance is Ted Leonsis (pictured here), one of AOL’s most colorful top early execs and a longtime inspirational figure within its ranks.

Unlike most AOL execs from those days, many of whom were eventually run out on a rail, Leonsis also stayed on through its disastrous merger with Time Warner and beyond.

But, like all of the Dulles complex–which was once the bustling worldwide HQ for AOL–Leonsis finally left the company, after a falling out with the management regime that Armstrong just hipchecked out of power. He is now AOL’s vice chairman emeritus.

Both CEO Randy Falco and President Ron Grant moved AOL’s locus largely to New York, and minimized the staff and influence at Dulles, where most of AOL’s products have been made since its origins in the early 1990s.

“It’s a smart move to go to [the Dulles staff] directly first…the last regime pretty much shut them out…and that created bitterness, when we need to be unified,” wrote one AOL insider to me in an email.

(Sidenote: As the AOL beat reporter at the Washington Post back then, I actually went with then-PR head Jean Case to look over what became the Dulles facility, to see if it would be a good place to expand to; previously, AOL was located in nearby Vienna, behind a car dealership.)

A Leonsis visit at AOL will be like old home week, although some are hoping too that former AOL CEO Steve Case could also make an appearance. He and Leonsis still make online investments together.

But that might still be deeply controversial within Time Warner, where Case and also former Time Warner CEO Jerry Levin are widely blamed for situation that the company found itself in when the Web 1.0 bubble burst and AOL’s once vaunted valuation collapsed.

Although Case and Time Warner CEO Jeff Bewkes have since moved on, bygones have not been bygones within Time Warner.

And, while it is often denied by top execs, AOL has suffered because of ill-hidden grudges, which have partly prevented it from being revived, even as other Internet giants have been born in the interim.

Ironically, many of the current crop of shooting stars owe a lot to the pioneering and innovative AOL products, including: its AIM and ICQ instant messaging services, which echo an early version of Twitter; the “Buddy List,” which was all about friending; and its deep social networking roots, with chat rooms and profiles that were the Facebook of its day.

The question for Armstrong is: Can AOL go home again?

Time Warner online unit AOL is cutting 700 employees due to the weak economy and the ensuing falloff in advertising revenue, but also because of recent structural changes made to refocus the once-mighty service.

AOL CEO Randy Falco sent a memo this afternoon to AOL staff about the layoffs and other cost cuts being made, confirming the moves.

The 10 percent reduction in workforce will take place over the next several quarters, with most of the U.S. layoffs to be completed by March. AOL has 7,000 employees world-wide, mostly located domestically.

AOL is also eliminating merit raises, just as Yahoo (YHOO) and other digital companies have done recently, and consolidating facilities.

While Time Warner (TWX) has been trying to sell AOL to Yahoo, the online unit has also been shifting its resources, as part of a long-term turnaround plan. It has focused the company on three parts: its Platform-A ad unit; its communications and social-networking arm, People Networks; and its recently launched MediaGlow content studio.

It has also been in the midst of splitting out its longtime access business, which has provided the bulk of AOL’s revenues and profits, which sources said has given its top execs insight into what its future business model should be.

Besides the layoffs and cost cuts, sources said AOL was also looking at paring its international business, which has never been particularly successful.

As part of its ongoing moves to make New York its main HQ, AOL will also be consolidating facilities in Silicon Valley, Los Angeles and at its original homestead in Dulles, Va., although not closing it completely.

Much as throughout the online advertising industry, AOL has seen drastic declines in growth. In a recent financial report, AOL said its ad business dropped almost 20 percent year over year.

And AOL’s worth has also declined, with Google (GOOG) recently writing down its 2005 investment of $1 billion in the online service, which valued it then at $20 billion. It is now valued at $5.5 billion.