Noticed this also appeared in one of the other parts of the forum so I'll offer the same thoughts here. I think people might be all over the place on this one since they get parts from so many different places and piece them together. I would think the easiest to do is something like this:
http://www.coolerguys.com/840556090885.html. I just built a 'son of' last week and lucked out because a friend of mine own a computer repair shop and he gave me a old pc temp controller, fan and power supply for free. Just a piece of advice. If you have not yet bought your insulation board go to your local Lowes, Menard, Home Depot, whatever and look for a sheet that is dinged up. If it's serviceable for your project ask for a discount. I picked up a sheet of 2" board for 1/2 off. With the free stuff from my friend and 1/2 of the carcass the total cost of my build...$15.22. Best of all the whole thing work divinely!