Nature's Miracle is easy to use, dries quickly, removes almost all of the odor (works better for dogs than cats). It has also stained 2 of my carpets and is a bit expensive.
To use, just pour it on the urine/fecal stain. Within 4 days the area is dry. Within 2 weeks the odor is gone. Cover with tin foil with holes poked in it to discourage pet from resoiling the area. It seems to be more effective on dog and female cat urine than male cat spray. On particularly humid days, a faint odor may still be detected in treated carpets. Also fades fecal/vomit stains, but doesn't completely remove them...