I have found that chlorine dioxide is very effective at killing mold in the air and on surfaces. It doesn't remove it so you have to follow up with a good cleaning.
You can find micro chlorine dioxide generator packets that are effective in about a 500 square foot area for about $20.
Ozone also works, but at the concentrations needed to kill mold it damages the items in the house.
I prefer to kill off the mold without doing damage, so after trying both I have settled on using chlorine dioxide.