CryptoTE - CryptoTE is a text editor with integrated strong cryptography.
Milanote - Milanote is a note taking app for creative work.
Paranoia Text Encryption - Paranoia Text Encryption encrypts text according to a choice of strong algorithms.
Notebook PEA - Protects your private notes with a password.
SilentNotes - A note taking app which respects your privacy.
Sec Notes - An android app for writing and storing AES-128 encrypted notes.