CryptoTE - CryptoTE is a text editor with integrated strong cryptography.
Google Keep - Capture notes, share them with others, and access them from your computer, phone or tablet. Free with a Google account.
GitJournal - Manage your Notes from any Git Repo.
Daybreak - An intelligent to-do app that learns when to remind you
Quillnote - Take beautiful markdown notes and stay organized with task lists.
Notebook PEA - Protects your private notes with a password.