I have a Desert Springs drum humidifier (they call it a rotary disc humidifier) and it works great. Second house I've installed it at, this unit been going strong for 7 years without replacement parts, etc. Very happy with it. Just a cleaning couple times a year is all it needs.
Basically a plastic drum made up on tiny wafer discs that have pores in them. And it constantly rotates and the drum dips back into the water as it goes round picking up water. The hot air is forced through the wafers and evaporates the water into the air.
Generally comes with a electronic valve that drains/refills the water (you can do it manually too) every couple days, so there is really minimal water usage.
