Here is a great tip from creativebits. Stickies and the Mac have gone hand in hand for years. They're a great way to quickly jot down a bit of information, just like their paper counterparts.
Ivan explains how to keep a Sticky Note front and center. With your target note selected, simply press Command-Option-F and it will float above all other windows.
Stickies have matured over the years, and gained additional functionality like appear translucent and display Quicktime movies.
What's your favorite "Sticky Trick?"