RealNetworks' games business grew revenues 33 percent since the first quarter of 2007. CEO Rob Glaser thinks it could grow even faster on its own. RealNetworks announced today it plans to spin off the casual games business and "may precede the spin with an initial public offering and sale of up to 20 percent of the shares," according to a press release. RealNetworks will also buy back $50 million worth of stock.