Yahoo's hopes to compete with Google and Microsoft in search and online advertising may be a fantasy, but the Internet company is a market leader when it comes to fantasy. Fantasy sports, that is. For those of you who haven't joined the rotisserie leagues, the object is to rack up scores based on the individual stats of imaginary teams made of real players. Not only does Yahoo have a much larger share of fantasy traffic than traditional sports properties ESPN and CBS, but, according to Compete, its lead grew this year with the opening of the 2007 NFL season (football is by far the most popular fantasy sport).