A friend of mine wanted to set up a small home network rack in his basement, but needed to do it as inexpensively as possible. We already had most of the normal equipment you'd set up in a home system - the modem provided by the cable company, an older (but still operational) Linksys WRT-54GL router and WiFi access point, and some other odds and ends.
In order to get it all set up, I needed a small rack. Craigslist was the first choice for this type of item, and browsing revealed a number of different items available. I settled on a Cooper half-rack on wheels, which I picked up for $50 (It fit in my car.) It appeared to have had some sort of high-speed fiber termination in it, as there were a couple of fiber patchpanels, and some Cat6e cables hanging out as well. A cable management rack was included as well, but the plastic had been shattered and it was discarded. I kept as much of the extras as I could, which was mostly just the Cat6e cable. These were about 1' long, and I set them aside for later. Pretty much everything else in the rack was discarded, as it was chopped or broken.
In order to add some good functionality to the rack, I located a seller with a slightly used rack-mount UPS (in a nice carpeted rack box) for another $50. Another Craigslist find, the seller was moving and wanted it gone. The PDU above it was a demo from some local company that had dead LEDs in the display - these were easily replaced. An AVTech RoomAlert 32e, left over from another job where I was able to purchase 3 of these units for under $50 was mounted as well, with some of the homemade sensors I described earlier. A discarded D-Link 10/100/1000 switch that was recovered from a junk pile at work after a switch upgrade was bolted in. Shelves were purchased surplus. Full of holes, but who cares? A Monoprice patch panel and some keystones rounded out the project.
We made some new cables with new wire and ends to run through the house, but I also reused all of the Cat6e cables that came with the rack. These turned into jumpers between the patch panel and the switch.
The rest of the equipment in the rack was already owned. Two Synology units and the aforementioned modem and router. As payment for setting things up, I requested co-lo on my own Synology unit, which along with it's accompanying APC UPS, makes a nice off premises backup system.
It's not the prettiest thing in the world, but it keeps everything in one place, and allows for airflow and offers a little bit of expansion if needed.
In all, the project totals, for things we didn't already have:
Rack and Jumpers: $50
Patch Panel: $20
Room Alert device: $20
Cables and misc: $100 (we didn't use all the cable for this job.)
TL;DR: When setting up a small system, Craigslist and eBay can be your friend.