While watching videos on the Internet or reading a document, it’s very annoying to have your Mac automatically dim the screen. Of course we can change that in the preferences but it’s such a hassle turning it back on or off.
Caffeine is a tiny application (240 KB) that puts an icon in the menu bar which can be clicked to prevent your Mac from automatically going to sleep, dimming the screen or starting screen savers. Clicking it again turns it off. It’s that simple!
I really like this application (for Mac) Keycue; it helps you to use the Mac OS X applications more effectively by displaying a concise table of all currently available menu shortcuts.