I'm using a Cohiba cigar box (unaviable in the states for obvious reasons...)
a filled box had costed about 650 euro, but i got it empty and for free. 
I'ts quite big, about 25x20x5cm. I've made the solder side of the arduino flat with some hot glue and attached velcron so the arduino can be taken of the lid. Yes, i've attached the breadboard and Arduino to the lid, so in closed position the stuff is hanging. the bottom of the box is filled with spare wires, resistors, ic's, leds and the like, and of course the usb cable...
When the box is opened the lid is under a angle so the Arduino and breadboard are easy accessable. Very transportable. if i have to move the setup, i only have to disconnect the varous sensors and externals.