My MBP 2.4GHz, Folding@Home running with close to 100% on both cores all day:
CPU A -- 71˚C
GPU Diode -- 68˚C
GPU Heatsink -- 60˚C
Heatsink A -- 55˚C
Heatsink B -- 45˚C
Enclosure Bottom -- 36˚C
Memory Controller -- 54˚C
Hard Drive -- 40˚C
This is sitting on a desk with less than ideal ventilation. Just to give an idea of non-idle temperatures.