In a quiet fund-raising effort, Ning has raised $15 million more, a round that is valuing the social networking start-up at an eye-popping $750 million valuation.

In its last fundraising $60 million round a little more than a year ago, Ning was valued at $500 million.

The money for this fifth Series E round comes from a Silicon Valley venture firm, Lightspeed Venture Partners.

The Palo Alto, Calif.-based Ning, founded by well-known entrepreneur and Ning Chairman Marc Andreessen and CEO Gina Bianchini, confirmed the funding when contacted by BoomTown. It was not actively searching for funding.

Other investors in Ning include LinkedIn Chairman Reid Hoffman, Legg Mason, and Allen & Co.

The additional funds raised bring the total garnered by Ning to $119 million.

Ning is a platform aimed at offering customizable tools that let users create their social networks about their interests, such as for fans of the movie “Twilight.”

Ning puts online ads on the sites, using Google (GOOG), and is also working on its own advertising platform. It also offers an array of other services and is planning more soon, such as a virtual-gift offering.

Founded in early 2007, it currently has 29.3 million registered users, who are using 1.3 million social networks, and it is adding one million registered users every 15 days, said the company.

But not all its social networks are active, and Ning’s monthly unique visitors are lower, according to various surveys, at about six million in the U.S.

Ning is one of Andreessen’s angel investments, although he recently raised $300 million for a new venture fund he is running with longtime investing partner Ben Horowitz.

In an interview, Bianchini said the goal was to become an even bigger platform for building social networks and the money would be used for possible acquisitions and other strategic options, attracting more talent and also to offer its social networks more tools to be discovered.

“It’s clear to me when you look the market…there needs to be a place for people to express their interests and passions,” said Bianchini, who noted Facebook and Ning do not necessarily overlap. “We want to be the social network for interests and passions online.”

Lightspeed’s Ravi Mhatre, who led the investment for the venture firm, said it was due to a lot of reasons, although he noted that the effort was not a traditional fund-raising effort, but more of an interest by Ning in adding a top VC to its investor pool and by Lightspeed in Ning’s hyper-growth.

“The growth at Ning has been massive in the last year and, combined with the quality of the team and seeing that kind of momentum, it worked out well for us both,” said Mhatre.

A few weeks ago, when I was having breakfast with legendary Silicon Valley entrepreneur Marc Andreessen about his new venture fund, he talked about what he thought was critical to being successful as an Internet company.

Ticking off names, from Apple (AAPL) CEO Steve Jobs to Facebook CEO Mark Zuckerberg, Andreessen said he always favored technical entrepreneurs for one key reason: “You need someone who lives and breathes product.”

It’s a refrain I have heard a lot recently from a wide range of people in the sector, most especially when talking about two of the more challenging renovations of key Internet brands going on of late.

That would be: Yahoo and MySpace.

In recent days, the focus at both Yahoo (YHOO) and MySpace, a division of News Corp. (NWS), has been on cost cuts, management rejiggering and, of course, layoffs, as new leaders at each Web giant are trying mightily to push the reset button. (News Corp owns Dow Jones, which owns this Web site.)

No surprise, their efforts have gotten a lot of attention and have been the subject of a lot of coverage (here for Yahoo and here for MySpace).

But, as those clean-up efforts wrap up, both have to show a whole lot more than that if either is to truly succeed at their tasks–which is to make both services much more relevant and exciting in the fast-changing Web arena.

While Yahoo and MySpace remain huge Web properties–and Yahoo, in particular, is very profitable in comparison to most Internet outfits–the widespread perception across the digital sector for too long now is that they are both tired in some significant ways and in desperate need of innovation.

Their big tasks include an overhaul of product offerings and features, a refreshing of brand and, most importantly, a strategic rethink that will set them on a new course for the next several years.

This is not a new thing in the Internet space, which has seen once-popular companies fall by the wayside as their products have gotten dull and consumers weary.

AOL–the Time Warner (TWX) unit whose new CEO, Tim Armstrong, is trying to reinvigorate that iconic but deeply tarnished brand too–is the classic example of this problem. But there have been too many that either hobble along, get subsumed into a larger company or just wither and die.

Sudden death is not likely to be the case for either Yahoo or MySpace, but time is most definitely running out for the pair to show some true product pizzazz and a strategic road map.

At Yahoo, most of the glitter thus far has come from the personality and charms of CEO Carol Bartz (pictured here), who has been hard at work projecting an image of moxie and decisiveness in her efforts to get some momentum at the turmoil-plagued company.

Replacing former CEO and co-founder Jerry Yang, Bartz has largely been busy cutting staff, pruning products that she recently dubbed “space debris” and rounding out her executive staff.

She’s also been prepping a new branding campaign to accompany Yahoo’s overhauled front page, which is set for the fall.

But, as the famous Peggy Lee song (see video below) goes: “Is that all there is, is that all there is?/If that’s all there is my friends, then let’s keep dancing/Let’s break out the booze and have a ball/If that’s all there is.”

But breaking out the booze and having a ball is actually not such a bad idea. To my mind, instead of tweaking what is there and emphasizing what it has been, Yahoo now has the chance to just go for broke and boldly make some dramatic choices.

That is especially true if it forgoes a search and online advertising partnership with Microsoft (MSFT), since Yahoo is going to have to do more than just what it already does better.

Interestingly, it is Microsoft, with its well-reviewed new Bing search service, that seems the most aggressively innovative these days.

So, why not, for example, make a shocking move, say, into the premium online video space? Yahoo certainly could pick up some damaged goods, like Veoh and Joost, on the cheap.

But what about buying the early winner: Hulu?

While the three studios that are its joint owners (the fourth owner is Providence Equity Partners)–News Corp., Disney (DIS) and GE (GE) unit NBC Universal–don’t seem inclined to sell, many sources close to the company said they most certainly would for the right price and perhaps a stake in Yahoo too.

Yahoo has been one of Hulu’s many distribution partners, but that effort has been lackluster. As owner, it would surely point its vast traffic and tech resources at Hulu to good effect.

In this kind of scenario, Google (GOOG) and Comcast (CMCSA) are also contenders for Hulu, but it is only Yahoo that has the truly better record of being able to create, manage and distribute Web content.

Plus, you could call it: HuHoo or YaLu or, better still, HooLu.

There are lots of ideas along these lines for Yahoo, but the overarching idea is to dominate in areas its rivals do not.

For MySpace, which was the dominator until rival Facebook cleaned its clock and then some, it is both a crisis of identity, a broken consumer experience and technology that needs a major overhaul.

It is hard to say what MySpace is, except really noisy. While the music part of that is good, the idea of making it hip again seems well-nigh impossible.

But it could be useful as an entertainment hub where it is fun to be. News Corp. CEO Rupert Murdoch raised this concept recently, in fact, and it is a good one.

That’s because Facebook is aggressively un-fun, with a fascist design sensibility and a thick ethos of utility and enforced busy-ness. Whenever I use it, I always start to feel like I am 23 minutes late.

There really is no good overall and unified entertainment hub on the Web in a massive way–one that aggregates all kinds of interests. I would, for example, love a place where I could easily live in a “Gossip Girl” universe.

Best of all, such a direction moves MySpace well away from Facebook, where is needs to get pronto.

MySpace CEO Owen Van Natta (pictured here) said as much in a memo to employees yesterday:

“As I’ve said before, simplifying and unifying our site is fundamental to our success going forward. MySpace should feel like one platform–not 15 sites loosely stitched together. We consider our diverse content offering a strength but too many logos and disorganized verticals makes the site difficult to navigate and creates confusion about our brand identity. Our users don’t know if we’re a social portal, a music site, or an entertainment hub.”

In her own memo last week, Bartz also talked about the need for speed and definition of Yahoo:

“I’ve noticed that since the reorg, people seem like they’re waiting for something. I’m not sure if it’s a sugar-low or what, but we need to stop waiting and get moving. Good things do not come to those who wait, they come to those who make things happen.”

Actually, per Marc Andreessen, good things come to those who make things. Wonderful things, fun things, memorable things and, if you are Steve Jobs, just one more thing.

Let’s just hope in the case of Yahoo and MySpace, they don’t settle for just any thing.

Until they do that thing they do, here is a catchy video from the movie, “That Thing You Do”:

Yesterday, shares of Netflix got their semiregular rocket boost–with its stock up more than five percent to close at just over $42–from rumors that Amazon was interested in buying Netflix.

Oh, it’s a seemingly dreamy match–the top online retailer snapping up the upstart U.S. mail-order DVD movie and television show service.

But the speculation completely ignored the giant price needed to buy the Silicon Valley-based Netflix (NFLX)–well above its current $2.43 billion market cap, to be sure–which would be a big chunk of Amazon’s $35 billion valuation.

And it also leaves out the nearly impossible tax problem Amazon (AMZN) would acquire if it ever bought Netflix, given that Netflix has many U.S. distribution locations for its subscription rental business. Amazon does not like paying state taxes and avoids them carefully.

Instead, those interested in seeing the independent company in the embrace of a larger one might want to consider a more suitable and very interested candidate: Microsoft.

Neither Microsoft (MSFT) nor Netflix will comment about such a hookup.

But several sources close to Microsoft told BoomTown that that the partnership between Netflix and Xbox Live to allow users to watch movies and TV episodes on the Xbox 360 device–struck exactly one year ago today–is going like gangbusters, with one saying it was “en fuego.”

Very loosely translated: On fire.

So much so, several sources said, that Robbie Bach–who is president of Microsoft’s Entertainment and Devices division, which includes the Xbox business–has been meeting with Netflix CEO and co-founder Reed Hastings (pictured) in recent weeks about what else the pair can do together to expand its current partnership.

The deal already in place between them is a hit, according to sources at both companies.

It gave Netflix access to 12 million Xbox members and handed Microsoft what has turned out to be a very popular application and an unusually successful joint effort.

While an acquisition would be a much bigger move, some at the software giant think it would necessarily be such a bad one for Microsoft, which has long been seeking to forge better ties in the entertainment arena.

Many of Microsoft’s major Hollywood forays over the years have been duds. So, stronger ties with Netflix–even a more robust partnership, at the very least–would give it a more definitive video strategy most think it lacks.

Its archrival, Google (GOOG), has been trying–with similarly lackluster impact–to accomplish the same results via its pricey and money-losing YouTube unit.

But Netflix–which has an office in Beverly Hills, as well as Los Gatos, Calif.–has much better relationships with the industry there, mostly because it has become such a big buyer of DVDs as it has grown its business (see charts below of subscriber and revenue growth; click on them to make them larger).

In addition, it has added more subscribers than ever in the last year and is solidly profitable, mostly due to sending consumers all those DVDs in little red envelopes.

And while a lot of execs at Hollywood studios that Netflix does business with have been wary–and told me so in no uncertain terms on my recent visit to Los Angeles–about its entry into the digital video delivery business, they have also been thrilled with the checks that Netflix has been writing them since it was founded more than a decade ago.

But, it is that main DVD business that Hastings, in a recent interview with The Wall Street Journal recently, has said is “doomed.”

Noted the article:

“As soon as four years from now, [Hastings] predicts, the business that generates most of Netflix’s revenue today will begin to decline, as DVDs delivered by mail steadily lose ground to movies sent straight over the Internet. So Mr. Hastings, who co-founded the company, is quickly trying to shift Netflix’s business–seeking to make more videos available online and cutting deals with electronics makers so consumers can play those movies on television sets.”

With Internet video still in its infancy–and barely in gestation in terms of any viable business model–Netflix might indeed need help, especially since Hollywood has been slow to give it rights to more movies for online distribution.

That will be increasingly troublesome, given that digital delivery is the way consumers are headed. According to the Journal story, over 20 percent of Netflix members now use the streaming service.

But it only has about 12,000 titles–mostly older films–licensed on its online service, compared to 100,000 DVD rental titles.

That’s because, for now, much more powerful pay channels usually win out over Netflix in these online video distribution wars, which also include Amazon and Apple (AAPL), along with many others.

Thus, even with a strong and unusually long-term executive bench, the close-knit Netflix will still be facing a major battle in moving in a direction it must head in sooner than later

Such an epic journey could be easier for Netflix with a powerful ally like Microsoft.

One more interesting link would make such a relationship even smoother: Hastings is also on the board of Microsoft, having joined in 2007.

So, the savvy and innovative entrepreneur–well-known for his close-to-the-vest dealmaking and eager to not miss a key turn for his company–might very well decide to keep friends very close.