Before i add further suggestions, let's sum up what we found out so far:
1.) Like
cristox said, there is no need to download anything, if you want to work with the commandline.
The
shutdown.exe shipped with windows does it all
2.) If you (like me) are to lazy to use the commandline, there are a lot of
UI-tools, which might be more convenient to use.
DShutdown,
Switch Off,
PowerOff and
ShutdownPro are just a few of them.
Besides providing a GUI for the shutdown they add further possibilities like shutting down at a certain time.
(You can also do this via commandline, but you would have to calculate the seconds left until the wanted shutdown-time by yourself

)
other suggestions:3.) As i do not want dozens of small programms to start with windows, i use my
ir-remote-cotrol-software which autostarts anyway.
i predefined a few commandlines (60mins, 30mins, immediatly, ...) using the
shutdown.exe and just have to activate them with my remote.
4.) Similar to this you could predefine commandlines for the
shutdown.exe in
foo_runto activate them from within foobar.
Additionally you can add buttons to your foobar-layout which use these foo_run-commands.
an
idea/suggest/request that just came to my mind:
a shutdown-plugin for foobar (using the shutdown.exe) which offers possibilities like "shutting down after finishing the current playlist". i have no idea if the effort doing this is in any relation to the use of such a plugin...just an idea....
Edit: another feature for a sleep-timer-plugin would be to decreasingly fade down the volume after a certain time to a specific volume before shutting down (like it is possible in mediamonkey e.g.).