Sergey Biryukov

Allows to find all posts where a particular attachment (image, video, etc.) is used.
Adds a “Used In” column to the list view in Media Library, as well as to the attachment details modal.
Finds posts that use the image (including any of its intermediate sizes) in post content, or as a featured image. Works with custom post types too.
Inspired by a <a href="http://wptavern.com/the-problem-with-image-attachments-in-wordpress" rel="nofollow ugc">WP Tavern post</a> on image attachments.

Find Posts Using Attachment

Allows to find all posts where a particular attachment is used.

John Luetke

Allows you to change the author of a piece of media by adding a drop-down list of all your blog’s users to the “Edit Attachment” screen in the Media Library.

Media Author

Allows you to change the author of a piece of media

Find Posts Using Attachment vs Media Author