consider undervolting the processor. If done properly, it can reduce power consumption, which means the fan won't be on as much. However, it is a long process that can be difficult. For more info, check:
This guide is pretty good, but personally, I prefer centrino hardware control over rmclock.
Dell just quoted me a more than a month's London rent for their new duo processor, good spec Inspiron 9400 with a 1900x1600 screen - amazing given that most laptops have 1280x800. It's meant to be very quiet. That is really NB to me. I returned the Inspiron 6000 to them for refund as it was so noisy I couldn't work. That had a Pentium M processor, supposedly "quiet".
The duos are new out. I can only wait a few weeks but do you know if they are quieter?
Otherwise what is quieter, Athlon or Intel Centrino/M as I guess prices will drop for 'old' processors when the duos hit the stores.
ciao, thank you.