Here's what he did in his own words:
Screw a foldback clip to your desk to create a document holder which is off the desk. That means you're using space that you never had — air space!
That won't work with enormous heavy documents, but is great for a handful of papers you need to refer to. In a similar vein, alisneaky has also rigged up speakers upside-down in the top part of his desk, making better use of the available space:
Neither hack is complicated, but both represent a neat way to get more use out of a standard generic computer desk. Thanks alsisneaky!