Found the Raspberry Pi a while ago, first time I have found time to post on the subject.
I’m using the Pi’s as server type devices for my Home Automation projects & other interests. so I had a need to put several Pi’s in my rack & a way to hold them successfully. I found that geekroo.com has several mounting options for the Pi & the one that allows you to stack several together. Their Aussie Bone 2.0 has a stacking plate to allow more that one Pi to be stacked.
Below is a mock up photo of the stack showing four Pi’s stacked together, headless with Wi-Fi access & powered via a USB hub. The photo below it shows the stack installed into my rack.
You only need one Aussie Bone 2.0 & then one stacking plate for each additional Pi to be stacked.
Also pictured is my Freetronics.com EtherTen that collects currently four temperatures from around the house & posts them to the MQTT Raspberry Pi Server in the stack. Next is to have the Raspberry Pi Pancake Web Server also in the stack, display the MQTT data on a page for integration into the house control pages, currently on a XP box below in the rack, soon to be moved to the Pi stack.