Over in the comments of Paul Kedrosky's blog, Paul and I were talking about Google's $345M capital expenditures in Q1 2006.
Assuming that capex is mainly for buying commodity servers, that works out to roughly 100k-200k new servers in Q1 2006. Paul says he thinks the lower end of that range, 100k or so, is more likely.
Either way, wowsers. That is quite a cluster they are building.
See also my previous posts, "200k+ servers at Google and growing" and "In a world with infinite storage, bandwidth, and CPU power".
See also my previous posts, "Google Sawzall" and "Google Cluster Architecture".
Update: Two months later, John Markoff and Saul Hansell at the New York Times report that "the best guess is that Google now has more than 450,000 servers spread over at least 25 locations around the world." [via Don Dodge]