TaskAgent

View and edit your to-do lists from anywhere. Because TaskAgent syncs your lists as plain text files through Dropbox, you’ll always have access to them. But if you just wish to keep your lists in the app, that’s okay too.

TaskAgent features:
-Interactive list interface: simple and easy to use
-Powered by plain text files: view and edit your lists even from outside the app
-Dropbox sync: your lists will always be there for you
-All tasks can be assigned an optional note
-Hotkey for quick task input
-Support for multiple lists
-List archiving option
-Task sorting options

Also available: TaskAgent for iOS