Google Keep - Capture notes, share them with others, and access them from your computer, phone or tablet. Free with a Google account.
Encrypted Notepad - Encrypted Notepad is a very simple to use application providing state of the art...
Daybreak - An intelligent to-do app that learns when to remind you
Notebook PEA - Protects your private notes with a password.
Paranoia Text Encryption - Paranoia Text Encryption encrypts text according to a choice of strong algorithms.
Cypher Notepad - Easy, Simple, Secure and Free!