I recently had a cronjob that was sending me a bunch of useless emails. When I’d open my Mac’s Terminal, I was greeted by a "You have mail.", message (I feel like it’s the days of AOL). I wanted to delete all of these messages in one swoop, and it’s actually REALLY easy to do.
My home server uses mdadm software RAID for my media share. The array is made up of ten disks, so it only seemed natural to spin them down to save power when our family wasn’t home. Powering them off when they aren’t in use should also reduce the case temperature, hopefully increasing the lifetime of the hard disks.