Monitor Off Utility

Monitor Off Utility is an energy-saving and system automation tool. It allows you to send your monitor to stand-by mode whenever you want.

Rather than waiting for the system to be inactive for 5 minutes before sending it to stand-by mode, you can use this application to give your monitors a better longevity and save some electricity along the way. So, you can create shortcuts that will turn off your monitor. You can even set a delay before the monitor is turned off. A countdown will appear in a box and you can cancel the operation before it is completed. You can always move the mouse and the monitor will turn on again.
Monitor Off Utility also allows you to lock your computer, instead of turning your monitor off. When you do that, the system will become idle as well. The good thing is that you can do all actions via hotkeys, which are customizable. Besides, you can activate your screensaver with a shortcut as well.
Another extra feature is that Monitor Off Utility can be run on the portable drives, which makes it very useful for the notebooks' owners, although I don't think you'd be turning your monitor off a lot when you go on the road.
In addition, if you run your computer all day long, you can set the program to turn the monitor off when Windows starts.