You can make a sticky note quickly and easily from selecting text and then going to the application’s menu (named for the application, between the apple and the File menu) and selecting Services and then Make New Sticky Note. It works in Safari, Mail and many other applications. In Safari, you can also use Command+Shift+Y. This is a quick way to capture bits of information for later use.
Related: Screen Capture a Window, Screen Capture From Mail, Google Search On Selected PDF Text, Replying With Selected Text, Quitting Several Applications.
