Also might want to check out the Garage Journal http://garagejournal.com/ it is a sister site to the HAMB. Tons of great ideas over there for setting up a new shop, home made tools, flooring, HVAC, Electrical, etc.
Here is a thread which discusses what I think you are talking about.
http://garagejournal.com/forum/showthread.php?t=141247&highlight=cooling%2Acompressed%2Aair
Here is another where a guy used an AC condensor (which are rated to 250-300 PSI) behind the Pulley/Fan on his compressor and re-routed the lines from his compressor to the tank to run through the condensor before it enters the tank. When the compressor runs the fan pulls air through the condensor cooling the air before it enters the tank.