Nice little free utility – MonitorES (Monitor Energy Saver).  Download this tiny (85k) utility and whenever you lock your PC, either by WinKey + L or by Ctrl-Alt-Delete, it will automatically switch off your monitor as well, thus helping to save the planet.  Added festures also include the ability to pause all media programs, set your IM status messages to ‘away’ and auto-start with windows so it runs every time you start windows.  If you need to, you can also use Ctrl + F2 to just turn off your monitor.

This should be standard on all PC’s in my opinion.