This is my take on running multiple computers in a single IKEA Helmer drawer unit. It has been done by several before me: render cluster. A difference from the various versions I have seen is that I use a single PSU to drive several small Mini-ITX boards (with plenty of power to spare). Also I have no intention to run the computers clustered but as several separate servers on different physical networks to fulfill my home network needs.
The top drawer hosts a PSU that was kindly donated by a friend of mine. The sides of the Helmer provides just enough space to do the cabling in a nice way without much effort. I have strapped the cables to perforated steel strips near the front of the drawers which makes it easy to use the drawers while the cables are connected. This makes it extremely easy to do maintenance and mount new hardware. If the cable is disconnected the drawers can easily be removed for more extensive adjustments.
The four middle drawers each host a Mini-ITX PC. Each drawer has a panel with power on switch and power LED. One of the drawers has an additional slot for a network card for running firewall and NAT. Another drawer has internal mountings for four 3.5" disks for serving files.
The bottom drawer has power but is not yet populated. As for now it is a nice place to keep all the manuals, documentation and plans for the build.