Michael Black wrote in
xample.org:

For larger boxes, computer power supplies offer up nice boxes. Cover any
side with the wrong holes with circuit board

You do like some rough-and-ready boxes! Normally I hate them, but one
very nice exception is old rack units. There are things so cheap on eBay (and
audio junk wherever it might be had) that is valued far lower than the box
it's in is worth. In this case a blank panel bought on eBay can make an
awesome case. One of my computers is based in one. ITX, 1.2GHz, should be fan
cooleed, but I made it totally silent, rack only 18cm front to back, 1U. All
kinds of very high quality work can be based on old rack units, whose
original innards may well be chosen for some otherwise expensive, rare and
exotic spares too.