Seattle-based real-estate information site Zillow has filed initial paperwork to kick off an initial public offering. The company hopes to raise $57 million, and will use the investment for general purposes, such as working capital, sales initiatives and so on.  Zillow’s prospectus is underwritten by Citi, Allen & Company, Needham & Company, ThinkEquity and First Washington Corp

“The filing is a little surprising. While it was rumored that the company was talking to bankers, its nearest privately held competitor, Trulia, has been more vocal about its plans for an IPO, and presumably would have been the first to file.”

In the filing, Zillow has disclosed its 2010 revenues, which have increased by 74 percent to $30.5 million compared to the previous year. It also reduced its net loss, from $12.9 million in 2009 to $6.8 million in 2010. Moreover, in addition to its IPO plans, the company is also set to receive a total of $5.5 million from Technology Crossover Ventures and PAR Investment Partners.

A bit earlier, Zillow as well as its competitor Trulia, rolled out their latest series of apps for the iPad and Android.  IBM is also pushing on the real-estate IT front, and announced its plans to buyout Las Vegas-based real estate management software developer TRIRIGA. Still, real-estate is not the only area which has entered the IT IPO season.

Video delivery firm Envivio noted in an SEC filing it hopes to raise as much as $69 million in an IPO. The company stated its revenues totaled $30 million last year, which is about twice the amount it reported during its previous fiscal year. The company’s net loss was $2.5 million or roughly a quarter of what it was in 2009, and plans to invest the funding in growing its employee base, among other things.

Another company who is heading towards an IPO is Millennial Media, the world’s largest independent mobile ad network. The company plans to double its staff by nearly 50 percent.