Is there anyway to mount the Mac mini "Core" on the bottom of a shelf in an entertainment cabinet? Could doing so harm the system?

As noted elsewhere in the Mac mini "Core" Q&A, Apple warns that you should not "put anything on top of your Mac mini or stack Mac minis on top of each other".

Placing something on top of the Mac mini could reduce the signal strength of AirPort (Wireless) and Bluetooth, and potentially interfere with proper cooling.

However, provided that you leave enough of a gap between the bottom of the shelf and the top of the Mac mini to allow proper cooling, such a space-saving installation should not harm the system. In fact, there are products designed to make it easy to attach your Mac mini to the underside of a shelf.

Photo Credit: Hubbell Automation

Three "bottom of a shelf" Mac mini mount kits are available from Cinnamon Peripherals, Newer Technology, and Hubbell Automation (pictured) -- the CinnaRack for Mac mini, NuShelf mini, and Mini mount Shelf 2, respectively.

All three have been reviewed by the excellent 123Macmini.com, and each review should be read in its entirety for the full perspective provided by the author, but in particular, the website was concerned that the CinnaRack:

Is approximately the same height as the Mac mini. Even with the included felt risers installed, the gap between the top of the Mac mini and bottom of your desk or shelf is really small. This could possibly lead to a decrease in Airport reception in some instances, depending on the location of your wireless router.

The Cinnamon Peripherals website notes that the product currently is being redesigned, possibly to allow for more space for cooling and wireless reception. The new version is reported to become available in "October 2006".

The only drawback mentioned for the NuShelf mini is that "it's still possible to push the Mac mini out of the mount if you press on it too hard" when connecting a USB device, for example. For the first version of the Mini mount Shelf, the reviewer only griped that it cost US$49.95, more than the other two.

For the Mini mount Shelf 2, Hubbell notes that the company has:

Changed a few things around to give you a stable, secure surface that attaches to the underside of just about any horizontal surface. Tables, shelves, desks, even the occasional Mac-mini-in-a-car project.

Hubbell also explicitly mentions that:

The design allows for airflow around the entire computer while also making sure there is enough clearance for your bluetooth and WiFi signals to get through.

Certainly a simple but elegantly designed product. If you're not the type who would prefer to rig your own mount with a piece of plywood and a handful wood screws, you probably would find it to be well worth the price.