Rich Text Editor for Excerpts

gistfile1.php

<?php
function lb_editor_remove_meta_box() {
	global $post_type;

	// Check to see if the global $post_type variable exists
	// and then check to see if the current post_type supports
	// excerpts. If so, remove the default excerpt meta box
	// provided by the WordPress core. If you would like to only
	// change the excerpt meta box for certain post types replace
	// $post_type with the post_type identifier.
	if (isset($post_type) && post_type_supports($post_type, 'excerpt')) remove_meta_box('postexcerpt', $post_type, 'normal');
}
add_action('admin_menu', 'lb_editor_remove_meta_box');

function lb_editor_add_custom_meta_box() {
	global $post_type;

	// Again, check to see if the global $post_type variable
	// exists and then if the current post_type supports excerpts.
	// If so, add the new custom excerpt meta box. If you would
	// like to only change the excerpt meta box for certain post
	// types replace $post_type with the post_type identifier.
	if (isset($post_type) && post_type_supports($post_type, 'excerpt')) add_meta_box('postexcerpt', __('Excerpt'), 'lb_editor_custom_post_excerpt_meta_box', $post_type, 'normal', 'high');
}
add_action( 'add_meta_boxes', 'lb_editor_add_custom_meta_box' );

function lb_editor_custom_post_excerpt_meta_box( $post ) {
	// Adjust the settings for the new wp_editor. For all
	// available settings view the wp_editor reference
	// http://codex.wordpress.org/Function_Reference/wp_editor
	$settings = array( 'textarea_rows' => '12', 'quicktags' => false, 'tinymce' => true);

	// Create the new meta box editor and decode the current
	// post_excerpt value so the TinyMCE editor can display
	// the content as it is styled.
	wp_editor(html_entity_decode(stripcslashes($post->post_excerpt)), 'excerpt', $settings);

	// The meta box description - adjust as necessary
	echo '<p><em>Excerpts are optional, hand-crafted, summaries of your content.</em></p>';
}