I'm looking for a plugin that will allow users to put

I'm looking for a plugin that will allow users to put arbitrary content at the bottom of every post (NOT every single page + post, just every post).

If there was a plugin that created another widget area for the bottom of a post before the discussion area that would work, or just a text field where you could put in arbitrary HTML / short codes to be rendered out above the discussion would be fine as well.

Is there anything out there that does this?