Alexa Web Search - Top 500
Currently number 74, as of this writing, according to Amazon.com's Alexa.
They also have a free toolbar for IE. Seems like everybody has one of those these days.
They claim that "This is the most useful toolbar ever made." Wow. Pretty strong assertion that I think a lot of people may not agree with.
I only mentioned the toolbar because I'm pretty sure that's what they are using to compile their statistics.