I have my late 2011 15 in hires antiglare MBP sitting on two pieces of molding. One on the left and one on the right. They raise the machine about 3/8 inch off my desk so air can get underneath it. My old machine was a 2008 Macbook and it used to run a little hot so I just kept up the habit of leaving some space between my Mac and my desk. When I've worked on the machine, I've noticed it was "warm" but never really "hot." I don't do CPU wasteful stuff like folding proteins (which used to keep my fans maxed out 24/7) or running CPU-intensive screen savers. I also allow the machine to auto-sleep after 4 hours. All of these add up to a cool-running MBP, no external fans or fancy gadgets required. Just 2 leftover pieces of wood corner molding about 11 inches each.
