There are also some pre-built fogger setups out there if you don't want to DIY it. You'd still need your own Humidistat though.
This vid shows the output difference between the Prefab 10, 5, and 3 Head foggers made by Nutramist:
http://www.youtube.com/watch?v=4oAQh8kH94E
The boxes that the foggers are in are basically what I described previously. They have an auto-fill ability to keep the fogger at the right depth, a fan that blows into the box, and you can attach a hose for the fog output.
In Hydroponics, more is better so I usually apply as many fogger heads as I can. In a Humidor setup though, I would think less is more. Most humi systems rely on normal evaporation to avoid wild swings in humidity. Active systems just apply a fan to speed up evaporation. A 10 Head fogger could have a foot of thick fog floating on the floor of 5'x6' room within a couple minutes.
Even running one for 15 seconds could cause a room that small to shift 5-10% RH. By the time the Humidistat recognized that the target % has been achieved to shut the fogger off, there would still be a bunch of fog evaporating.
I'd just recommend a single head fogger unless you're looking at 1000 Cubic Feet or more. Then you could
maybe bump it up to a 3 Head. I'd probably still stay at 1 head for anything but a warehouse though.