I work in a computer store building PCs all day. With every new case there are one or two 8cm case fans included. Most of the systems we build do not need any more cooling than is supplied by the CPU fan as most of our customers generally don't go in for all this "overclocking malarky".
Looking around the stock room I discovered two large boxes of unused 8cm case fans.
Surfing through case mod sites, the most popular mod you see (besides Lexan windows) is some form of whizzy cooling device, be it fan or waterblock. People go to great lengths to keep their PCs cool.
Now...Puttin these two things together...
Edit:Thumbnaails done...