Facebook, the dominant internet social networking company, is making plans to go public early next year at a vertigo-inducing valuation of over $100 billion, CNBC reported Monday. The Palo Alto-based web phenom could file registration papers with the Securities and Exchange Commission as early as October.

Wall Street titan Goldman Sachs, which managed a $1.5 billion dollar private placement in Facebook sharesfor non-U.S. investors earlier this year, is “leading the chase” to manage the offering.

Goldman Sachs, the premier investment bank on Wall Street, is accustomed to taking the lead slot on such pricey offerings, which usually involve as many as half-a-dozen banks or more. As underwriters, Goldman and the other banks are allocated chunks of pre-IPO shares for their hedge fund and institutional clients, many of which sell their shares at the open for a tidy gain.

In January, Facebook said it expected to cross the critical 500-shareholder mark this year, and if it finishes 2011 over the line, it must file quarterly and annual reports with the SEC within 120 days after the end of the year. At the time, Goldman, which had invested $450 million in Facebook, said the company was worth $50 billion.

Today, Facebook is trading at an implied valuation of $80 billion on private, secondary markets like SharesPost, where employees and early investors sell shares to “accredited investors,” including banks and individuals worth over $1 million.

Meanwhile, Groupon, the fast-growing but money-losing Chicago-based online coupon service is raising eyebrows over its creative accounting methods ahead of its $750 million IPO.

Facebook’s IPO could be the biggest internet offering in over a decade. Already this year, ZipCar raised $174 million and watched its stock price close up 60 percent in its first day of trading. Demand Media, which went public in January, enjoyed a 33 percent first-day pop. Groupon recently priced a $750 milion IPO and social gaming firm Zynga is expected to announce an offering soon.