An engineering solution from one of my fellow students at Waterloo is to have a large container of cooler-than-air water at a high level. Get some copper pipe, run it from the water container in a spiral in front of a fan, then have it empty into a lower container (or out your window).
As the water runs in front of the fan, it will absorb heat energy from the air. The pump is powered by the height difference between the container and outside. Efficiency can be increased by adding more surface area to your copper pipe to facilitate heat exchange.
http://www.eng.uwaterloo.ca/~gmilburn/ac/geoff_ac.html
Edit: Beaten.