Believe it or not, it can be as simple as using wet towels! Evaporating water will always create cool air, so the only requirement is to create a simple, continuously evaporating sheet of water, which is easy to convert into your own refreshing supply of continuously cool air. A ready-made swamp cooler would probably cost you the same as a conventional air conditioner at your local appliance store - between $100 and $300. But knowing the secrets of swamp coolers make it even easier to build one yourself!
The final ingredient is usually just an ordinary electric fan, which blows the cool air in the right direction. And there's lots of different ways to accomplish this. Instead of hanging wet towels in front of the fan, one inventor suggested instead pointing the fan over a cage filled with wet hay. ("Warning...eventually the hay will get moldy, so replace it.") And another entrepreneur even built a solar-powered swamp cooler using a pile of moist wood chips and some fans from old computers!
However you decide to build your swamp cooler, remember that it's considered a very "green" technology. Swamp coolers indirectly harness the power of the sun, since it's heat in the air that's causing the water to evaporate. While they'll still using some electricity, swamp coolers will always be more environmentally friendly than a typical electrical air conditioner, because they use far less electricity to generate cool air.
Besides all their other advantages, they're also cheaper to run! One Phoenix man turned to swamp coolers when the afternoon temperatures climbed as high as 112 degrees, and he eventually just ran a garden hose through a portable misting tube that he'd bought at their local Home Depot for $13! He clipped the tubes to the front of a box fan, and it cool the temperature - even outdoors, so the sun wouldn't fry his garden. He was so proud of his creation, that he uploaded an online video documenting the simple instructions.
The popularity of swamp coolers has given way to a lot of misconceptions. (For example, one tinkerer tried using duct tape to strap an ice pack to the back of their fan!) And one entrepreneur is even selling "neck coolers", which involve a special gel that absorbs cool temperatures over a long period of time, and then releases it slowly.
But it's still possible to build a true swamp cooler using materials around your house. In fact, the ancient Egyptians used swamp coolers! (They'd soak linens with water, and then place them in the path of the prevalent northern winds, according to one web site). Even several hundred years B.C., long before the days of technology - people were already cooling their homes with swamp coolers!