Switch Off (free) is a handy utility that will lock, shut down, hibernate, or put your computer to sleep. It will also log off a user, kill a VPN connection, or run a script at a time you choose--including immediately. Of course, you can automatically hibernate or put your computer to sleep with Windows built-in functionality, but you can't automate the rest of the actions. And it's nice to have everything in one spot. With diligent application, you could save a fair amount of power by using Switch Off.
Switch Off sits in the system tray, or "notification area" as it calls it. Click the Switch Off icon, which looks like the standard on/off symbol, and you're presented with dialog that lets you schedule a task. Right-click and you're presented with a context menu full of actions that you can perform immediately or delay for 30 minutes, an hour, or two hours. You can also schedule tasks for after the same lengths of CPU inactivity. My only complaints--and they are decidedly minor--are that in the English version, the menu says "past 30 minutes" instead of "after 30 minutes," and running Switch Off at startup is unintuitively referred to as "pin to notification area."
Personally, I find Switch Off handiest for its single-step shut down. I hate having to click through the XP shut down dialog. However, I'd be remiss if I didn't inform you that you can do the same thing with a shortcut to Windows own shutdown.exe (the utility that Switch Off is most likely fronting) by entering "shutdown.exe -s -f -t 0" on the command line.
Everything in Switch Off worked perfectly, and you may also access the program remotely, though this will require you forwarding a port on your router to the PC in question. The program is lightweight, easy to use, and a nice extension of Windows functionality.