It happens to leave the computer on for hours and hours, forgetting to shutdown. But now with this small free software we can save some money from the electricity. Idle Monitor can Shutdown your computer if is not used. It based on mouse movements and can shutdown your computer for you, if left unattended for X number of minutes!
Even Shutting Down you can set to run an application or open a website. It has a adjustable idle trigger time up to 24h ( 24h=1440 min, 12h=720min)