My machine is a TiBook/800 and I'm lucky I don't have the loud fan problem (yet?). Fan usually doesn't kick on if the underside has a gap for cooling. If I'm on battery and put the machine on the arm of the couch, the fan will turn on every once and a while. At my desk though, I never notice it.

It was getting a little warm though the keyboard, so I picked up a Kensington "Fly Fan", a USB fan. With the rear of the laptop raised a centimeter, and the fan blowing down under the machine near the power plug, it never got warm to the touch.

But, the fly fan is a bit noisy, so I'm going to be picking up some cheap PC heat sinks (inch or less in height) and cutting/gluing them together into a laptop stand (to raise the rear up a bit for easier typing). That should allow for quite good passive cooling so I can use the fan at work instead. :)