One of my friends in my electronics class did a cool setup on his Xbox to keep it cool. He used the same idea behind a computer case.
You know how most computer have the one fan on the side of the case, with the bigger fan on the back of it? The side fan is sucking in the air and blows out the back.
Well he, he cut the metal grill out on the back of the Xbox case, and also cut out the plastic part of it too.
Then he went and bought 2 cheap used computer fans, about the same size as the ones on the side of a computer tower. Then he cut out 2 square holes on the top of the Xbox case and mounted the fans on top of the Xbox, just make sure to setup the fans so that they are sucking air into the Xbox, and make sure you are using a very good grill for the fans!