Take the approach Geohot is suggesting. Take a shipping container, make a standard layout, cooling and compute load. Find a cheap source of electricity.. Place it and have compute.
It has been done... We used to get our POP gear built out from Dell (?) in shipping containers - pre-racked, wired, and cooled - just add network/power feeds. We'd have them dropped places we needed more capacity but there wasn't space available in the DC.