In the wake of 4 million Dell batteries being recalled, Channel Nine had video of an iBook catching fire. Requires WMP 10, Real and IE 6. (But admittedly the kid was using it on carpet, which frequently causes some overheating as there’s reduced air circulation. Still, it shouldn’t catch fire). There are also photos of the iBook on fire here.
I also found some references to dodgy cables on Apple power adaptors (of which I’ve had several yo-yo adaptors sparking near where the cable meets the adaptor.)