With 4U or 5U height servers (this wasn't so long ago '08 - '09) we did some or all of the following:
Slowed CPU and backbus Unplug CD and Floppy power. Disable 2 of 4 PCI bay fans - moved PCI cards adjacent to remaining fans. Created a Power Profile to slow down or disable all unneeded on board peripherals: VGA, Parallel, Serial, Firewire, IR and USB controller. Disabled the above in BIOS if the option was offered. Converted a lot of 5-6 disk RAID 5/6 arrays to RAID 0/1 or variant preferred by the application owner (15k rpm drives replacing 7500 rpm units) A shell game of sorts was to shift the surplussed 7500 rpm drives to the spare pool for retiring servers (12 month or less remaining rack time).