First, Attic Fans
Attic fans designed to move air from your attic to the outdoors. Why would you want to do this? Well, a good handyman knows that in the summer, the temperature in an attic can reach 150F or higher in warm parts of the country. Sure, you have insulation between your living area and the attic, but in that type of high temperature, the heat conduction taking place is fairly significant. That means the rooms with attic space directly above them will be warmer than they need to be. How much warmer? 10F-20F warmer. Between a ranch and a two story, a ranch has a higher percentage of ceiling-to-attic area than a two story of the same square footage. Most estimates have houses in warm parts of the country saving 20%-30% on their electric cost (air conditioning) when using an attic fan. The only downside to an attic fan is really the installation. If you can't vent it out the side of your house you have to start cutting holes in your roof to vent air up and out. Any time you cut holes in your roof (and thus shingles) you're running the risk of water leaks and water damage unless you do things carefully, by the book.

Whole House Fans
The savvy handyman will recognize that a whole house fan has many of the same characteristics as an attic fan as well. By pushing air into the attic, it's forcing air out of it as well. That's a good thing. So why not just get a whole house fan instead of an attic fan? For one, you can't run a whole house fan at the same time as air conditioning. It'll pull all the cold air right out of your house. An attic fan will not, as it only draws air in through your soffits and vents while leaving the air in your living space alone. Installing a whole house fan can be as simple as cutting some drywall and running some electric, or as complicated as cutting and heading joists. Sometimes, if there's not enough venting in the attic for the whole house fan to push air through, it must be installed in conjunction with an attic fan.

Installing an attic or whole house fan is a great handyman home improvement project. Make sure you have the time and energy (and skills) before starting.