Summary

Printed indieflow's design but no dice with the fan I had! These grip a 12cm cooling fan on the outside edges if it has solid straight through screw holes (such as the cheap brushless fans from maplin).

Instructions

Print the long and short files, affix as shown in the photo. I would recommend running the juice from a reprappro huxley with melzi (19V) through a 12V regulator (L78S12 or equivalent). Wire into the fan socket on the melzi board and you can then control it automatically during printing using settings in slic3r or skeinforge. Tools are obviously only required if you'd messing with regulators!

Edit:
After a bit of use, I recommend sticking a big heatsink on the voltage regulator (2nd picture). This not only stops the fan slowing down as things heat up but also makes it look a bit more badass. If a fan can look badass, which it probably can't.

Huxley 12cm outer-edge fan mount