Fan Science

comair rotron
Still the best engineering info for fans and thermal design
cooling and noise
A good thermal design tutorial
fan noise solutions
An excellent site detailing several solutions that keep your rig cool and quiet at the same time
fan speed control
Good comparison of speed control techniques.
fan speed control is cool!
A great technical resource for fan speed control circuit designers
four-speed fan control
An app brief detailing a cheap comparator-based speed control approach.
general fan performance
Fan science 101--read this if you are needing a solid intro to air cooling
nmb tech
Another good thermal design resource
smart sensor
A good explanation of how fans work is tucked away in this article