Hi Jeff,

You have really interesting and useful articles, thanks for sharing your knowledge.

I've found a solution for displaying featured image on posts and pages admin columns with code pasted on you theme's functions archive. Just another way to achieve the same without adding a another plugin to your WP installation.

add_filter('manage_posts_columns', 'posts_columns', 5);
add_action('manage_posts_custom_column', 'posts_custom_columns', 5, 2);
add_filter('manage_pages_columns', 'posts_columns', 5);
add_action('manage_pages_custom_column', 'posts_custom_columns', 5, 2);

function posts_columns($defaults){
$defaults['riv_post_thumbs'] = __('Thumbs');
return $defaults;
}

function posts_custom_columns($column_name, $id){
if($column_name === 'riv_post_thumbs'){
echo the_post_thumbnail( array(100,100) );
}
}