I've been screwin' around with fanbus, rheobus, controller setups for quite a while now and finally decided to add one of the fun ones to my watercooling rig.
I first found the setup
here at hardware-corner.net if anyone's interested. It allows you to crank up a 12v fan to around 17v depending on the resistor you use...as well as turn it down to whisper quiet levels.
I built a ghetto-box and added a stock AMD fan to cool the LM317 that get's pretty warm.
..controller mounted with power, fan and cooling fan leads.