Running an iBook with the lid closed would be very handy. It's very irritating having to keep it open to play music - in the car or living room etc, or play a movie on a TV. I no longer have an iBook to test this (No, I didn't melt it) but I believe there's a way to get around the heat issue of running with the lid closed.

I think it must be possible for whatever triggers the sleep mode when the lid is closed to instead trigger a change of energy saver preferences - low cpu speed, screen off.

Also there is a file in the System folder (I researched this a while back and I can't remeber where it is or what it's called exactly) that sets the fan speed and the temperature at which it's activated at. Anyone with a newish mac which has OS controlled fans should be able to locate this file, I guess it's with the driver for the fans. It was certainly present on my iBook G4 12" 1.2GHz but isn't on my current PowerMac G4/533. I think it would be posible to set the fan driver setting so that the machine is kept cool enough while the lid is closed. Obviously if the fans are spinning it would decrease battery life somewhat and increase noise levels slightly.

I would be very interested to hear from anyone who has experimented with this as I think there's real potential. I'm going to try it next time I can get my hands on someone's ibook :)