Rackable Systems has announced immediate availability of their version of Sun's Blackbox data center in-a-shipping-container. Called "Concentro," it can house up to 1,200 systems, using Rackable's proprietary DC-powered server and disk hardware. See their website for more info: http://www.rackable.com/solutions/concentro.htm.
Last I looked at the Black Box, it appeared to be missing a couple of things. If I recall, it needed a chilled water supply and gen-set to be complete, and those would likely each add a container to the operation. To be cost-effective at N+1, you'd need to cluster them (e.g. five gen-set containers, four datacenter containers, and five chiller plant containers, and a diesel truck or two).
Also, there are some environmental concerns: opening the container doors when it's cold outside would cause condensation inside. So you'd need to build an environmental enclosure around the four datacenter containers. Maybe you could use one those inflatable golf driving-range quansit huts as a container for your four datacenter containers, and leave the chiller and gen-set plants outside.
Rackable Systems Announces Portable Data Center
