This is a simple plugin to dash encode a string (and convert to lower case) for ExpressionEngine. Create a folder inside your third_party directory with your sitename (all one word in lower case). Change all references of sitename in the file to your sitename.

pi.sitename.php

<?php  if ( ! defined('BASEPATH')) exit('No direct script access allowed');

/**
 * ExpressionEngine - by EllisLab
 *
 * @package  	ExpressionEngine
 * @author		ExpressionEngine Dev Team
 * @copyright	Copyright (c) 2003 - 2011, EllisLab, Inc.
 * @license		http://expressionengine.com/user_guide/license.html
 * @link		http://expressionengine.com
 * @since		Version 2.0
 * @filesource
 */
 
// ------------------------------------------------------------------------

/**
 * Energy Cell Client Plugin
 *
 * @package		ExpressionEngine
 * @subpackage	Addons
 * @category	Plugin
 * @author		Neil Bradley / The Energy Cell
 * @link		http://www.energycell.co.uk
 */

$plugin_info = array(
	'pi_name'		=> 'Sitename Helper',
	'pi_version'	=> '1.0',
	'pi_author'		=> 'Neil Bradley / The Energy Cell',
	'pi_author_url'	=> 'http://www.energycell.co.uk',
	'pi_description'=> 'Sitename helper plugin',
	//Ensure your sitename here is all lower case except the first character
	'pi_usage'		=> Sitename::usage()
);

//Ensure your sitename here is all lower case except the first character
class Sitename {

	public $return_data;
    
	/**
	 * Constructor
	 */
	public function __construct()
	{
		$this->EE =& get_instance();
	}

	/**
	 * Just encode a string to lowercase, replacing spaces with dashes
	 * @return Formatted tag is returned
	 */
	public function dash_encode()
	{
		// The Template class variable $this->EE->TMPL->tagdata contains everything between the {exp:sitename:dash_encode} tags in the template
		$tagdata = $this->EE->TMPL->tagdata;
		$needles = array(" ");
		$return_data = strtolower(str_replace($needles, '-', $tagdata));
		return $return_data;
	}
	
	// ----------------------------------------------------------------
	
	/**
	 * Plugin Usage
	 */
	public static function usage()
	{
		ob_start();
?>

Dash Encoding - converts spaces in a string to a dash and converts to lowercase;
{exp:sitename:dash_encode}{title}{/exp:sitename:dash_encode}

<?php
		$buffer = ob_get_contents();
		ob_end_clean();
		return $buffer;
	}
}


/* End of file pi.sitename.php */
/* Location: /third_party/sitename/pi.sitename.php */