If you live in a dry climate (I'm in Colorado), consider a swamp cooler. It's an amazingly simple and efficient machine: just a water pump and a fan, and peanuts in electrical costs compared to a full air conditioner. As long as you can establish airflow throughout the home, it feels just like A/C on days below 95F; you won't feel chilly on 95F+ days, but it's still quite livable.