Milanote - Milanote is a note taking app for creative work.
Encrypted Notepad - Encrypted Notepad is a very simple to use application providing state of the art...
CryptoTE - CryptoTE is a text editor with integrated strong cryptography.
StoryWall - Cards on a wall. But, like, totally digital.
Paranoia Text Encryption - Paranoia Text Encryption encrypts text according to a choice of strong algorithms.
Trello - Infinitely flexible. Incredibly easy to use. Great mobile apps. It's free. Trello keeps track of everything, from the big picture to the minute details.