The only thing I do to keep my PowerBook cool is if I'm viewing a flash-heavy website which maxes out the CPU, I sometimes go into the Energy Saver prefs and turn the processor down to "Reduced Power" - this usually results in a peak processor temp of around 53C, as opposed to 60+C
One of the main reasons for doing this is because my PowerBook acts as a brilliant radiator in my small room 😀 And sometimes I don't want to boil!