Mac only: Lots of us like to listen to music as we fall asleep, but if you usually drift off before hitting pause, iTunes will keep playing forever. If you don't feel like making short playlists, try using this handy Applescript.
Letting iTunes play throughout the night could drain your laptop battery, screw with your play counts, or worst of all, wake you back up. To stop these horrible things from happening, free Applescript iTunes Sleep Timer will stop iTunes playback after a certain amount of time, decided at the script's activation. All you need to do is download the script, drag it into your ~/Library/iTunes/Scripts folder (if it doesn't exist then create it), and activate it in iTunes by clicking the script icon in the menu bar. Your light-sleeping, techno-hating roommate will thank you.
iTunes Sleep Timer, is a free download, Mac only.