This is how I created a simple and effective cooling method for my PS3.
Step 1: Fan Choice
I chose this Thermal Take fan because it has a USB connection which means that I don't need an extra power supply. It plugs into my PS3 and is only on when the PS3 is on...PERFECT!
It also has variable speeds so when I need more cooling it can scale up.
NOTE: The fan really only has low and high speeds, not continuously variable like you would think with a potentiometer.
Step 2: Placement
I chose to put the fan in the top-right most corner of the media cabinet. This ensures it will remove all the hot air that rises from the PS3 and other electronics and is as out of the way as possible.
You can see that I simply removed the cover and drilled the bolt and main hole pilot while holding it in place (very carefully!) This was easier than marking it with a Sharpie and drilling the marks for me.
Step 3: Drilling
This is the fun part. For this 80 mm fan I used a 3 inch bit. This is almost perfect as it leaves enough room for the bolts to hold the fan to the cabinet while maximizing the area where air will escape.
80 mm = 3.14 inches
I got the drill bit at Lowe's for about $15.
Step 4: Install the Fan
I wanted to keep the metal covers on the fan because the fan blades are brittle plastic. I ran the bolts from the outside of the cabinet so that it would be flush and clean looking.
Because of the thickness of the wood on the cabinet the bolt did not reach all the way through both ends of the fan. I had to resort to zip-ties to hold the metal guard on the interior part of the fan. I won't be seeing this so it doesn't matter.
Step 5: Finishing
Once the fan was all hooked up and the area was thouroughly vacuumed I tested it out. The great part is that it only runs when the PS3 is on so I don't hear the fan 24/7. The PS3 used to get over 100ºF, which was not good for it's lifespan. Now the air in the cabinet barely gets above ambient. The fan has 2 speeds and low was sufficient for me. If I add a powerful receiver and surround sound I may want to go to the higher speed but we will see.
One bad thing is my PS3 does not have USB ports on the back of the unit so the wire runs all the way to the front. Not terrible, but not ideal either.
Hope this helps!
It was easy and totally worth it, BTW.