Here is a nice trick I learned the other day:
I triggered a Windows Update on a server last night but cannot reset it right now, since there are users that I don't want to kick off. So I just drop to command line and hit
at 03:00 shutdown /R /Y
The reboot will start at 3 in the morning and nobody gets hurt.
For more fine tuning be sure to check
(via GregorS, again)