Cold "brewing" your coffee decreases the natural acidity of coffee by 3/4 that of an average cup of coffee. This gives your digestive track quite a break, is better to keep your Ph levels in balance, and yet is still smooth and rich in flavor. You can buy a set for doing cold processing at home from Filtron with all the bells & whistles, but I like to limit my gadgets in the kitchen and instead use a French coffee press and simply use cold water and let sit for 24 hours.
From our I am Grateful recipe book: