Spotlight is a vastly under-used feature of OSX. It has numerous benefits beyond simply searching (much in the same way Google does).
The Apple Blog recently posted an article highlighting some additional uses of Spotlight. My favorite of which, is the calculator and dictionary functions.
To use Spotlight as a calculator all you have to do is type in an equation. You can do simple math, or complex equations using mathematical terms like square roots and so forth.
To use Spotlight as a dictionary, all you have to do is type in the word that you’re looking to define. The definition will pop up as a top search result. Simply select it and the full dictionary will open giving you the full definition of the term you’re searching for.
