They need little explanation: Ikea makes a cheap little table whose legs are exactly 19" wide and (barely) sturdy enough to accept screws and the weight of most rackmount equipment. (I wouldn't chance a loaded Apple Rac in it). Here's an orphaned photo posted to reddit featuring a typical example:
Eth0 entertains a specification and offers a fantastic IKEA-style manial for the Lack Rack. The most notable recommendation: use cavity screws to increase the load-bearing strength of the mostly-hollow legs if you're putting in machines more than 5cm down from the tabletop.
Its low-cost and perfect fit are great for mounting up to 8 U of 19" hardware, such as switches (see below), or perhaps other 19" gear. It's very easy to assemble, and thanks to the design, they are stable enough to hold (for example) 19" switches and you can put your bottle of Club-Mate on top! Multi-shiny LackRack can also be painted to your specific preferences and the airflow is unprecedented!
And of course the tabletop is perfect for placing a monitor or laptop, like the one in Frank Denneman's lab:
A little finish goes a long way:
Things sometimes get quite out of hand.