Another index card application for the iPad. I looked at Index Card in a previous post. I exports to "email, iTunes, or Dropbox as a formatted text file, image, PDF, or an Index Card Board file." It costs $4.99 (just like Index Card).
There is also a minimalist version called "index cards®", but it seems to have a rather limited feature set (and I don't like the registered sign behind "index cards"). It's just $0.99.
These applications seem to be inspired by Scrivener's cork board. They are designed for outlining, or perhaps better: pre-outlining, or moving around different passages or scenes before or while writing them up. They are not really designed for serious data storage, though they could perhaps be used for such purposes as well.