Tab Notes is a menu-bar application which keeps your notes tidy and easy to access, and your screen uncluttered. Click on your screen edge, and a note pops up!
This application is a menu-bar app: its icon does not appear in Dock. You can change preferences from the icon in the menu bar.
Note: The demo is version 1.9.4; the version available for purchase on the Mac App Store is version 2.1.5.