I really enjoy the clean operating space around my iMac but I always wished there was a way to mount my backup hard drive somewhere out of sight. I had seen a device called a "backpack" made for iMacs that serves as a shelf that juts out from the rear of the cast aluminum base. Nice as it was, it seemed a bit expensive and motivated me to glance around the house for another solution. Basically, this instructable uses zip-ties to form a harness for the hard drive. A separate zip-tie fastens the hard drive to the back of the stand. This trick should work for any moderately small form-factored hard drive (mine is a 500GB MyBook).
Step 1: Harness Your Hard Drive
The first step involves using two (or more) zip-ties to form a harness from which the hard drive will be suspended. I only had 8" zip-ties lying around the house, so I used a total of four to make the harness. Make sure that it's tight but still loose enough to thread another zip-tie underneath.
Step 2: Fasten Hard Drive to Stand
Once the harness is tightened, use one zip-tie (or more, if needed) to fasten the hard drive to the back of the display's stand. Thread the zip-tie underneath the harness zip-ties and tighten the fastener so that the hard drive is suspended at the preferred height. I placed the power/data connections facing down, and centered the drive just above the cable opening on the display stand.