I actually built about a year ago, and never bothered to post it. I mentioned it to a couple of people this week, and thought I would post it for them:
I had a couple of 2U servers laying around that I was planning on installing, but that's kind of a weird form factor for setting up around the home. Fortunately, we had some laminate boards laying around, left over from a water-damaged built-it-yourself stand-alone closet that was in the basement when we moved in. I tossed the water damaged parts, but held onto the rest of the boards, just for something like this.
I used 4 shelves, and built a box about the right form factor. I already had some casters (not shown in the photo, because they're underneath) so I attached them to the bottom to easily move the box around. The only parts that I ended up buying were the mounting racks for the servers. It's just not a part that I had laying around the house. It's also not a part you can find at Lowes, but it's easy to find online. I bought mine from Star Case. I figured that a 10U set should last me for a while.