Memrey - Advanced Notepad for Creative Minds
CryptoTE - CryptoTE is a text editor with integrated strong cryptography.
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.
Notebook PEA - Protects your private notes with a password.
wreeto - A simple workspace to help you focus.
Paranoia Text Encryption - Paranoia Text Encryption encrypts text according to a choice of strong algorithms.