Google Keep - Capture notes, share them with others, and access them from your computer, phone or tablet. Free with a Google account.
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.
GitJournal - Manage your Notes from any Git Repo.
OneNote - Get the OneNote app for free on your tablet, phone, and computer, so you can capture your ideas and to-do lists in one place wherever you are. Or try OneNote with Office for free.
Quillnote - Take beautiful markdown notes and stay organized with task lists.
RedNotebook - RedNotebook is a software that format, tag and search entries and add pictures, links and customizable templates, spell check notes, and export to plain text, HTML, Latex or PDF.