I truly wish I was in the mix when the Rocky Mountain Institute conducted a charrette in February of 2003, resulting in a series of design recommendations for data centers.
What a discussion they must have had, with a whole host of leading lights (Ken Brill, Peter Gross, Jonathon Koomey, KC Mares, John Pappas, Bill Tschudi...) among the ninety participants, from academia, the IT industry, utilities, and NGOs working on energy issues.
I suppose we might look back on the series of recommendations as a roadmap for the next seven years, and many of them have actually come to pass (like an EnergyStar standard for servers and the now common technique of isolating hot and cold air flow paths in data centers).
And, unlike some of my other reference library tomes, this one is available in the non-dead-tree version. With credit to RMI, here is the document (they apparently are not posting at their site any longer): Download HPDC_72