The unregulated secondary markets for late-stage private companies like Twitter, Facebook, and LinkedIn are quickly becoming a big business for fund managers and even retail investors.

    Chris Sacca is one of the super-angels -- a group of seed-stage investors who have raised third-party capital to find the next Facebook or Twitter. Not as well known, however, is that Sacca also has raised more than $30 million from outside investors to invest in Twitter, even at this later stage of its life as a private company.

    The money is pooled into a pair of funds called Industry LLC and Lowercase RT, and backed by a pair of institutional investors.

    So far, Sacca has put all of Industry LLC to work and is almost done with Lowercase RT. Both vehicles are able to buy up Twitter shares from employees and preferred stockholders, according to multiple people with knowledge of the funds.

    Sacca also considered raising a third fund called 140 – going so far as to send out offering docs to a small circle of prospects -- but seems to have since changed his mind. He declined to comment for this story.

    Investing directly in secondary investments of private companies is not new. There are several firms devoted to such deals, and even some burgeoning marketplaces for accredited retail investors.

    What Sacca and others are introducing, however, are pools of capital raised to buy existing stock in a specific private company. Fortune has learned that funds have been raised by other managers to acquire shares in such companies as Facebook, eHarmony, LinkedIn and Zynga.

    One of those other managers is New York-based Felix Investments, whose funds are believed to hold approximately two million shares of Facebook stock, according to a secondary market source.

    Felix was launched last year by former members of Advanced Equities, a firm known for raising money to co-invest with venture capitalists in new issues. It's not exactly for the masses, but it's as close as one can get given accredited investor requirements.

How the pool works

    A typical Felix process works as follows: The firm identifies a company with a large number of buyable shares, and designs a fund. For the sake of example, let's say the target is Zynga. Felix then goes about identifying investors. Much of the interest is inbound -- particularly from Silicon Valley technologists -- but Felix also pays a secondary marketplace called SharesPost to blast its offerings out to select members. Both and Felix and SharesPost confirmed this relationship but both declined to discuss specific fund raising, citing SEC restrictions.

    Those who participate only know that they are getting a chance to buy into Zynga, the hottest social gaming company on the planet. They are not given any non-public financial data on the company, because Felix doesn't have any. Investors also are not told the price at which shares will be purchased. Instead, their money is put into an escrow account while Felix goes in search of sellers. Once Felix figures out the price, it goes back to investors and gives them a chance to fish or cut bait. Most usually keep a steady reel.