Hasso Tepper has another power patch; this one to turn off PCI devices when the corresponding module is unloaded. This can make laptops cooler by turning off the sound or network, for instance. It has been commited, though you need to tweak a sysctl to enable it.
A running description of activity related to DragonFly BSD.
That really is a good move, I wonder if an idle network card or modem being disabled would save any juice.