Notability - note-taking and annotation app for Mac, IPad, and iPhone
OneNote = one place for all of your notes
Simplenote - Simplenote is an app that makes it easy to keep notes, lists, ideas and more. Your notes stay in sync with all of your devices. And it's free.
Google Keep - Capture notes, share them with others, and access from your computer, phone, or tablet. Free with your Google account.
