If you have problems with your PC locking or going to sleep, caffeine will keep it awake. It works by simulating a keypress once every 59 seconds, so your machine thinks you're still working at the keyboard, so won't lock the screen or activate the screensaver.
Annoyed by your screen turning off when you're using certain apps? Don't change your display settings and waste battery by keeping the screen on when the home screen is open. Just install this app and tell it which apps you want to keep the screen on for.This app doesn't have any features at the moment.
NoDoze simulates keyboard/mouse activity to keep the screensaver from activating. Its activity depends on currently running programs. You can use regular expressions or Windows wildcards to choose when the screensaver is deactivated.This app doesn't have any features at the moment.
PleaseSleep is a utility software designed for Mac OS X that helps put your computer to sleep when you know some other app is preventing your Mac from going to sleep.This app doesn't have any features at the moment.Discontinued
The developer has quit and the official site is gone except for a farewell message, but the site has been archived by Internet Archive: https://web.archive.org/web/20151202113600/http://www.dragonone.com/products/macosx/pleasesleep/
Prevents your computer from going to sleep, hibernate, dim the display or start the screensaver. Application runs in the system tray when closed. New in version v1.3: -Parameter support. v1.2: Option to let display fall asleep. v1.1: Sleep timer.