InventGeek.com have a created a guide to building a computer ion cooler. An 'ion cooler' is an electrostatically charged device that can propel air in a certain direction using electricity alone, no fans. Silent yes, the down side is that this cooler is based on a high power ion generator which puts out several thousands of volts, which can kill you.
The project is pretty straight forward, two wires strung across an old clear plastic case from a CD-R 50 disc spindle, one ion generator, a 12V power supply and a healthy dose of insulation.
By mounting the miniaturized ion cooler unit at the rear of a standard PC case, InventGeek say she unit draws enough air out of the chassis to keep it reasonably cool.
Do not try this yourselves folks.