Robert Scoble has posted some photographs he took of the new data centre belonging to Facebook while on a recent tour of the facility:
The data centre is located in Prineville, Oregon, and is claimed to be the most energy efficient in the World. Unfortunately, he shot the photos on a smart phone (why?) rather than a DSLR so they are a bit blurry in places, but it is still a fascinating piece non the less.
Updated 2022 : note that the above post was originally published in 2011, but is left here for archival purposes.