Stickies - Stickies is a PC utility written to replace Post-It-style notes left stuck to your monitor.
Evernote - Bring your life's work together in one digital workspace. Evernote is the place to collect inspirational ideas, write meaningful words, and move your important projects forward.
Scrawl - Scrawl is a notes taking and memo app that lets you keep track of the things that are important for you, like daily routine tasks, projects, reminders, calculations, or accountability of someone.
Standard Notes - A safe place for your notes, thoughts, and life's work
Pystickynote - Stickynotes for your desktop easily from the command line.
Joplin - Joplin is a free, open source note taking and to-do application, which can handle a large number of notes organised into notebooks. The notes are searchable, tagged and modified either from the applications directly or from your own text editor.