iOS: You won't find a shortage of note-taking apps on the iPhone. But if you're looking for something incredibly simple that syncs with services like Dropbox, Evernote, email, Twitter, or Facebook, then Squarespace Note is worth a look.
Squarespace Note is similar to the note-taking app, Drafts in that it acts like a place where you can store notes, but also send them off to other services. It doesn't have the wide support of Drafts, but it has the big services like Dropbox and Evernote (and Squarespace, of course). When you open Squarespace Note, you're taken directly to a blank page to type a note. Then you can swipe up to save the note to your phone, swipe right to send it elsewhere, or swipe left to look at your old notes. It's very simple, but if you want your note-taking app to act like a sheet of scratch paper on your desk, and not a full-fledged tool, Squarespace Note is worth a look.