Not to be outdone by hidden Windows 7's right-click menu options, Mac OS has its own set of hidden menu options for application and service icons in the menu bar. For example, if you click the audio icon, you typically get a volume slider bar. But if you hold down the Option key (aka the Alt key) and click the same icon, you'll reveal a list of available output and input device options, as well as a convenient shortcut to the sound preferences menu.
With the Battery icon, Option+click shows you the operating condition of your laptop battery, which gives you a sense of when you'll need to replace it. The four possible condition options are: Normal, Replace Soon, Replace Now, and Service Battery. It's a good way to either confirm or alleviate the suspicion that your MacBook battery may be near its end of life.
If you back up your Mac using Time Machine, holding Option will toggle a link to Browse Other Time Machine Disks in place of the normal Enter Time Machine function. From here, you can choose to recover backups from multiple drive sources. This feature can also be accessed from the Time Machine dock icon.