These ultrasonic units are very expensive http://futuregarden.com/hydroponics/systems_nutramist_gardens.html

However, you can build your own cheap substitue with a five gallon sterilite container, a hole saw, some foam ez clone replacement discs and one of these

http://crafters2000.stores.yahoo.net/ulfog.html

add a timer.

Total cost less than $50.

I know some want to start everything from seeds but if you are inclined to experiment this is a cheap way to try cutting edge cloning at a hatchet price.

The fog created by these units is remarkable.