This plugin lets you assign non-authors as post author.
Do you have a blog/website with a lot of contributing authors but you do not want to give them the rights to publish the articles themselves for whatever reason? In that case it would be nice when you are able to give them credit for what they wrote anyway. Since WordPress cannot override the author with a non-author by default, this plugin overrides the Author meta-box with a meta box that can select any user.
So whenever you want to place an article that was written by someone else, you just create a user with subscriber role (if he/she hasn't already) and assign the article to that user!