Each Raspberry Pi sits on a custom 3d-printed sled. The original model B/B+ and the Raspberry Pi 2 have an identical form factor, so it works for both!
Leftover breadboard jumper wires are connected to the GPIO pins the Pi to provide power, with the other ends glued to the sled. Power and ethernet are really the only connections I care about in this project, as the Pis will be ran headless. The Pi can be powered by these GPIO pins using any 5v source, but it bypasses protections on the usb micro power supply port, so care must be taken that the power supply is within what the Pi accepts, and polarity is correct. The Pi wants between 4.75V and 5.25V (less than this, or drops, can trigger the B's brown out detector - details here: https://www.raspberrypi.org/forums/viewtopic.php?t=58151)
The sleds are completely screwless - pegs printed into them fit the RasPi's mounting holes, and little clips hold the Pi in place.
This is my first adventure into 3d printing, and getting the sled just right took literally a dozen iterations. To figure out what my very low end 3d printer was capable of, figure out the easiest way to mount a Pi, how to run the power, etc.