noflushd

allow idle hard disks to spin down

Noflushd is a daemon that spins down disks that have not been read from after a certain amount of time, and then prevents disk writes from spinning them back up. It's targeted for laptops but can be used on any computer with IDE or SATA disks. The effect is that the hard disk actually spins down, saving you battery power, and shutting off the loudest component of most computers.