The Raspberry Pi does not come with a case. Is it safe to rest the device on any dry surface during operation?
For example, would it be safe to place a case-less Rasp Pi directly on the floor of a metal comms cabinet?
Would resting the Rasp Pi upon a conductive surface cause problems or prove dangerous?
You definitely want to keep it away from any conductive surface, to avoid damaging it. I am currently awaiting a case from adafruit.com . In the short term I have run it on an antistatic mat, and now it is in a lego case I created from my nephew's collection of legos (similar to this one).
Stay away from conductive surfaces, such as metal, it is very likely to damage your Pi and possibly other devices attached to the Pi.
I frequently recommend a piece of paper as a useful surface for running circuit boards on, but that is only a short term solution, something resembling a real case should be purchased in the long run.
No conductive surfaces - you run the risk of short-circuits.
I put some stick on feet on mine and stand it on a piece of paper.
Think of it as any other computer, you can but shouldn't, even if you were to suspend it by its wires the dust in the air could damage the board.
Don't put it on any conductive surface. Others have said this, but I see anti-static bags have been recommended!! Anti-static bags and coverings get this property by being slightly conductive. Great for transporting or storing circuit boards, but not for operating them.
As others note, use of a low resistance conductive surface is a bad idea.
Use of an entirely insulating surface runs the risk of electrostatic buildup which can damage PCB assemblies. The preferred solution is either a surface which is very slightly conductive and grounded, or supporting the PCB so no electrical contacts are made.
Spraying the bottom of the PCB with a conformal coating is a good idea.
This provides a degree of protection against contact but is more valuable as a protection against longer term contamination and as an ESD protection. There are numerous formal conformal coatings avail;able, but a cheap and reasonably effective coating is polyurethane clear "varnish" available in spray cans for general purpose surface coating purposes. The PCB top can also be sprayed if desired BUT all connectors and mating surfaces would need to be masked to prevent them being coated. Probably not worthwhile overall.
The box it came in makes a good temporary case, if you cut a few holes in the sides for the ports.
Don't run it on a conductive surface, that's a sure way of damaging the Pi, or at least making it unstable. You'll probably end up shorting random points on the board.
Any non conductive surface should be ok - plastic, wood, etc. if you're thinking of building a case should all be fine.
In the short term I'm running mine on the anti-static bag it came in which works a treat (I've run whole PCs this way with no issues.)