Well, I decided that I was too cheap to spend money on an expensive fan to cool my nano. Instead I went to fry's, bought a $3 computer fan, a $6 transformer, a $.5 dollar diode bridge, a tiny perfboard and made a fan. It is super easy to do, and costs less than $10. It works great. All you do is connect one side of the transformer to 120V ac, and the other to the two ac inputs on the of the diode bridge. Then you connect the other two parts of the diode bridge to the appropriate dc leads of the fan (+ and - are marked). Done and done. A warning to the wise, Do not run anything except a fan off of this power supply. The current is not perfect dc current, but rather a combination of ac and dc current that will not hurt the fan, (in fact fans are known to create this sort of current,) but will destroy anything else you try to power with it. A power supply for anything else is slightly more complex.