Even in the midst of a tough investing environment, Silicon Valley legend and serial entrepreneur Marc Andreessen (pictured here) and his longtime investing partner, Ben Horowitz, have completed the raising of a new venture fund, according to numerous sources close to the situation, and it is oversubscribed.

Sources said the fund–which was nicknamed “Project A” but is actually called Andreessen Horowitz–will be $300 million. It is $50 million over the $250 million he and Horowitz had planned.

Several major institutional investors–from universities, for example–have invested large chunks of up to $20 million or more, while a spate of Silicon Valley luminaries has put in amounts of $1 million or less.

The quick completion of the fund raising, in the midst of a national econalypse, is a good sign perhaps for the forward-leaning culture of tech, which has seen some pullback by VCs over the last six months.

Andreessen, who co-founded Netscape–the iconic browser company that was key to introducing the modern Internet to consumers–and a lot of other start-ups, announced on the “Charlie Rose” television show in February that he was creating the new fund.

“For the first time in my life, I am crossing over into the dark side,” said Andreessen at the time (see the video below).

Although he gave few specific details about the fund in that interview, Andreessen essentially said he was simply putting a structure around his own active angel investing, which has included start-ups like Twitter, Facebook, Digg, LinkedIn and many more.

Andreessen, who is on the board of Facebook and an adviser to Twitter, has turned into one the the digital sector’s most influential mandarins for innovative start-ups.

His new effort will focus on early-stage investments, he said in the interview with Rose, noting that “our claim to fame is, we’ve actually, you know, by entrepreneurs for entrepreneurs, we’ve done it, we’ve been on that side of the table for a long time; we know what it’s like.”

Andreessen said then that he and Horowitz had made 36 investments over the last three years of up to $200,000, but that his new firm will make up to $1 million bets on companies they decide to invest in.

Plus, he said then he would be patient: “Like with our new fund, if we fund a company today, we’re thinking about a return in seven to 10 years, so we can go through three or four or even five years of economic downturn, as long as, at some point, we come out the other end.”

Here is the video of Andreessen on the Rose show (he starts to talk about the new fund in the interview at around 18:33 minutes, again at 46:55 minutes and at the very end):

Last night, well-known Internet entrepreneur Marc Andreessen appeared on the “Charlie Rose” television interview show, talking about the digital sector and unveiling the news that he is creating a new venture fund.

I had heard rumblings about Andreessen’s funding efforts earlier this week, with sources I talked to nicknaming it “Project A.”

Actually, Andreessen said the new firm is called Andreessen Horowitz (zzzz), because he is doing it with longtime investing partner Ben Horowitz.

“For the first time in my life, I am crossing over into the dark side,” said Andreessen.

Although he gave few specific details about the fund, Andreessen essentially said he was simply putting a structure around his own active angel investing, which has included start-ups like Twitter, Digg, LinkedIn and many more.

His new effort will focus on early-stage investments, he said, noting that “our claim to fame is, we’ve actually, you know, by entrepreneurs for entrepreneurs, we’ve done it, we’ve been on that side of the table for a long time; we know what it’s like.”

Adding that he and Horowitz had made 36 investments over the last three years of up to $200,000, Andreessen said his new firm will make up to $1 million bets on start-ups.

Of course, for most of the interview, Rose zeroed in on hot topics like Facebook, the social-networking site on whose board Andreessen serves.

The voluble tech star did his job, talking about how Facebook could turn on the spigot and make all sorts of money anytime it wants and about the recent controversy around its Terms of Service kerfuffle.

He also talked about the Andreessen-backed Ning social network service, the Apple (AAPL) iPhone, Twitter, why the New York Times irks him, Google (GOOG), the Amazon (AMZN) Kindle e-book reader and gaming.

Ironically, the Netscape co-founder and his Xbox from Microsoft (MSFT)–eek–“have a very close personal relationship.”

But Andreessen also told Rose a little bit about the new fund he is raising money for, for example, while discussing the economic meltdown.

Talking about the fact that innovation will survive, Andreessen said: “Like with our new fund, if we fund a company today, we’re thinking about a return in seven to 10 years, so we can go through three or four or even five years of economic downturn, as long as, at some point, we come out the other end.”

Here is the video of Andreessen on the show (he starts to talk about the new fund in the interview at around 18:33 minutes, again at 46:55 minutes and at the very end):