A Netcraft June Survey shows that IIS is catching up to Apache quite well.
Neowin.net has the scoop.
Excerpt
"The number of hostnameson Windows servers grew by 4.5 million, giving Microsoft 29.7% market share, a gain of 4.25% for the month. Apache had a decline of 429K hostnames, and loses 3.5% to 61.25%"
Technorati : Apache, IIS, Netcraft