I decided one day to test my Clamshell, to see how hot I could get it. (obviously I wouldn't do this to any of my other computers).

iBook G3 466Mhz
256 MB RAM

Note: This is the Processor Temperature I'm talking about.

Normal temperature (virtually idle): 36 Degrees Celcius (96 F)
Standard Working Temperature: 48 Degrees Celcius (118 F)
Hard Working Temperature: 54 Degrees Celcius (129 F)

and then.....

I ran every application I had in my dock, all 24 of them. This included The entire Macromedia Sweet, Office apps, everything.........Photoshop, illistrator etc. While loading I managed to start a disk scan with TechTool also.

The temperature was then 72 Degrees Celcius (162 F), and just after I took that reading, my iBook went into serious Kernel Panics, and took about 10 mins to cool down during startup. Since it has no fan, it used the CD drive to help it cool down by spinning it really fast.