A swamp cooler is definitely a good investment if you live in a dry area like the southwest. Evaporative coolers use much less electricity than a standard air-conditioning unit, and have the added benefit of adding moisture to the air when it is dry.
Many people will have both a air-conditioning unit and a swamp cooler to get the best of both worlds.
Swamp coolers only work when the air is dry, if it is raining, or very humid than they do not work.
That being said they are still sometimes installed in humid areas since they bring in clean-air from outside which builds up a slightly higher air pressure in a home or business which makes the air always feel fresh.
Evaporative Swamp Coolers
Champion Cooler 4001 Dd Down Draft Duct Evaporative Cooler, 4800-Cfm Evaporative (Swamp) Cooler
Champion Cooler N46W 4200 CFM 2-Speed Window Evaporative Cooler
Champion Cooler AD1C5112 MasterCool 5000 CFM Down-Draft Roof-Wall Media Evaporative Cooler with 3/4 HP Motor, 12-Inch