Bare CentOS 5.8 install over the weekend.
When I mean bare, I mean disabling all packages in the installer; just linux kernel, init scripts, bash, networking. I had no idea that this would mean no ACPId, which meant nothing happened when I pushed the power button.
yum install acpid
# ACPID config to power down machine if powerbutton is pressed, but only if # no gnome-power-manager is running event=button/power.* action=/sbin/poweroff