Adding this to your functions.php will allow you to use custom field values in your post via short code.

custom_field_shortcode.php

<?php

/*
@description: 	Adding this to your functions.php will allow you to use custom field values in 
		your post via shortcode. Useful for when you need to add javascript to a post.
@usage: 	[custom_field name="name_of_custom_field"]
@returns: 	Custom Field Value
@author: 	Byron Rode
@license: 	Free to use, modify, whatever.
*/

if(!is_admin()) add_action('init', 'tgr_add_shortcodes');
if(!function_exists('tgr_add_shortcodes')){
	function tgr_add_shortcodes(){
		add_shortcode('custom_field', 'tgr_register_shortcode');
	}
}

if(!function_exists('tgr_register_shortcode')){
	function tgr_register_shortcode($atts){
		global $post;
		
		// defaults
		extract( shortcode_atts( array('name' => ''), $atts ) );

		if($name == '') return;

		$post_id = $post->ID;
		$custom_fields = get_post_custom($post_id);

		if(!empty($custom_fields[$name][0])){
			return $custom_fields[$name][0];
		}
		
	}
}

?>