Right click on desktop, create new short-cut.
Type shutdown.exe -i
Click next, type in name for your short-cut e.g. shutdown computers
Run the short-cut you just created. Now you can browse the network for computers to shutdown/reboot etc. or just type in the IP/Name of the computer.
You can even broadcast a message, and schedule the shutdown.
Cool for sysadmins.
NOTE: You will only be able to shut down computers that you have admin access on!