I´m mounting a board with Raspberry Pi, Arduino, USB HUB for Rasp Pi, the 5V regulator and an adjustable regulator.
I used screws and plastic brackets (like a ring) to secure the boards.
To feed circuits, I use a source of 12V /1.25 A which is connected to the Arduino´s connector .
Beneath the Arduino (the power connector) I soldered wires to feed the regulators with 12V.
With the output of the 5V regulator made a direct link under the Raspberry Pi (using the internal fuse).
Even with 5V I plugged my USB HUB modified. I made a direct link within the Hub, so that he does not use the 5V Raspberry Pi. The cool thing is that the Hub has power switchs for each USB port.
The LM317 adjustable regulator (1.2 to 12 VDC) feeds power to the breadboard circuits.
See the photos on Flickr:
http://www.flickr.com/photos/jgustavoam ... 650634969/
Gustavo Murta (Brasil)