display-post-id.php

<?php
add_filter( 'manage_post_posts_columns', 'pm_add_col' );
function pm_add_col( $cols ) {
	$cols['post_id'] = 'ID';
	return $cols;
}

add_filter( 'manage_posts_custom_column', 'pm_display_col', 10, 2 );
function pm_display_col( $col, $post_id ) {
	if ( 'post_id' == $col )
		echo $post_id;
}
?>