Easiest way to cool 10 gallons or more is with a copper wort chiller. Go up to ebay and type in "wort chiller" and you've get a ton of results. Same with "copper wort chiller" and "plate chiller".
I got one where it's just a copper tube in a circle that you hook up to your kitchen faucet. All ya have to do is stick it in the wort, turn on the water and stir.