Here's what I do for humidity hides - my corn & ball python LOVE em...they're in 40 & 70 gal tanks though, this wouldn't work for smaller enclosures & rack systems I guess...
Sterilite plastic shoe box with lid. Soaked & squeezed-out sphagnum moss inside. Hole cut in the end (& smoothed round the edges of the hole) for access. Lid on, it stays moist for ages & fresh for quite some time. Actually I stack two in each tank, under the heat lamp. That way the top one, nearer the light, is warmer, & the bottom is cooler. If they absolutely get cold, they can bask on top the box if they want to (not usually).
So there's half my hides right there - I like a warm-dry, cool-dry, warm-moist, & cool-moist. The corn burrows through the moss & the fatty-loaf ball python mats it down
Other stuff I have for hides at the moment are:
cereal boxes
cracker boxes
frozen veggie boxes
oatmeal canisters
paper towel tubes
CD rom drive box
kleenex boxes
US priority mail boxes (the flattish ones)
.....you get the idea. It's not very pretty...I started out wanting pretty & maybe I'll return to it when we're living elsewhere...but it's free, recycled, & they can poop/pee on stuff & I can just throw it away & replace it. They seem to like the variety, too, cause it changes.
-Kimhotep