Marcus Downing

Adds an “Identifier” column to the All Posts and All Pages admin panels, and to any custom post types. 
This column goes just after the Title column and shows each page’s slug, indented if necessary.

Page Identifier Column

Adds an "Identifier" column showing a post of page's slug, just after the Title column.

Aaron Butacov

Adds a [post_thumbnail] shortcode for use with wordpress post thumbnails. Size can also be set using [post_thumbnail size=”XXXX”]. (You can call the function directly in your theme with <code><?php post_thumbnail('size=thumbnail');?></code>.)
Just insert the shortcode into any post’s content and when it will be replaced with the featured image.
This works only with the featured images introduced in WordPress 2.9.
For more information head to the full information page for <a href="http://aahacreative.com/our-projects/wordpress-post-featured-image-shortcode/" rel="nofollow ugc">WordPress Post Thumbnail Shortcode</a>.

Insert Featured Image Shortcode

Adds a shortcode to insert the post's featured image into the post's content.

Page Identifier Column vs Insert Featured Image Shortcode