The gist: Out-of-warranty rackmount servers can often be purchased very cheaply. The major downside to deployment outside a data-center (for instance, in one's garage) is the noise.
I would like to collect suggestions for creating effective noise-dampening/baffling for 1U, 2U, and 3U rack mount servers using cheap, readily-available materials (this is the key constraint). Links to plans with pictures would be ideal.
I was able to drastically reduce the noise from my recently-purchased ($60) HP Proliant DL-145 1U server by forming a sleeve from an inflatable foam sleeping pad, but I would prefer solutions that use waste-materials such as cardboard and polystyrene.
Also welcome are recommendations as to which types of rackmount hardware are quietest (I now know that 1U servers are the noisiest due to their small fans) and tips about other ways of reducing noise such as details on how to reduce fan speed with specific server lines. Criticism of the wisdom of trying to make noisy hardware quiet ok too.