WriteNext - The writing application that boosts your writing. Increase focus and writing performance and reduce distractions by separating your creative writing from other activities. Let writing be the only activity you perform in the writing application.
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.
Calmly Writer - Distraction-free text editor for Mac, Windows, Linux and ChromeOS.
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.
Stashany - Online notepad for developers
Google Keep - Capture notes, share them with others, and access them from your computer, phone or tablet. Free with a Google account.