iOS: The new widgets in iOS 8 add all kinds of great functionality. If you want a notepad in there too, Neato does the job.
Neato works with both Evernote and Dropbox. Pull down the Notification Center, write a note, and send it off to the service of your choosing. You can also tweet, send an email, or a text message. Neato isn't an actual notepad app — you have to use either Evernote or Dropbox to use it. It's a pretty simple app, but having a notepad in Notification Center is super helpful. Plus, the app's free for a limited time, so grab it while you can.
Neato (Free) [iTunes App Store]