Originally pasted at http://code.garyjones.co.uk/wordpress-sitemap-class/

sitemap.php

<?php

/**
 * Allows XHTML sitemap to be added
 *
 * @package GT_Sitemap
 * @author Gary Jones
 * @version 2010-05-19
 * @since 2010-03-20
 */
class GT_Sitemap {

	/**
	 * @var string
	 */
	protected $_pagesText;

	/**
	 * @var string
	 */
	protected $_postsText;

	/**
	 * @var string
	 */
	protected $_archivesText;

	/**
	 * @var int
	 */
	protected $_headingLevel;

	/**
	 * @var array
	 */
	protected $_order = array( );

	/**
	 * @var bool
	 */
	protected $_showPageDate;

	/**
	 * @var string
	 */
	protected $_showPostDate;

	/**
	 * @var bool
	 */
	protected $_showPostCount;

	/**
	 * @var string
	 */
	protected $_archivesType;

	/**
	 * @var string
	 */
	protected $_pagesDateFormat;

	/**
	 * @var string
	 */
	protected $_postsDateFormat;

	/**
	 * @var string
	 */
	protected $_customPagesQuery = '';

	/**
	 * PHP5 constructor, setting defaults
	 */
	public function __construct() {

		$this->_pagesText = 'Pages';
		$this->_postsText = 'Posts';
		$this->_archivesText = 'Monthly Archives';
		$this->_headingLevel = 3;
		$this->_order = array( 'pages', 'posts', 'archives' );
		$this->_showPageDate = true;
		$this->_showPostDate = 'published';
		$this->_showPostCount = true;
		$this->_archivesType = 'monthly';
		$this->_pagesDateFormat = get_option( 'date_format' );
		$this->_postsDateFormat = get_option( 'date_format' );
		$this->_customPagesQuery = '';

	}

	/**
	 * @param string $id
	 */
	public function setPagesText( $id ) {
		$this->_pagesText = $id;
		return $this;

	}

	/**
	 * @param string $id
	 */
	public function setPostsText( $id ) {
		$this->_postsText = $id;
		return $this;

	}

	/**
	 * @param string $id
	 */
	public function setArchivesText( $id ) {
		$this->_archivesText = $id;
		return $this;

	}

	/**
	 * @param array $id
	 */
	public function setOrder( $arg1, $arg2 = null, $arg3 = null ) {
		$this->_order = func_get_args();
		return $this;

	}

	/**
	 * @param int $id
	 */
	public function setHeadingLevel( $id ) {
		$this->_headingLevel = $id;
		return $this;

	}

	/**
	 * @param string $id
	 */
	public function setPageDateFormat( $id ) {
		if ( 0 === func_num_args() ) {
			$this->_showPageDate = '';
		} else {
			$this->_pagesDateFormat = $id;
		}
		return $this;

	}

	/**
	 * @param string $id
	 */
	public function setPostDateFormat( $id ) {
		if ( 0 === func_num_args() ) {
			$this->_showPostDate = '';
		} else {
			$this->_postsDateFormat = $id;
		}
		return $this;

	}

	/**
	 * @param string $id
	 */
	public function setDateFormat( $id ) {
		$this->setPageDateFormat( $id );
		$this->setPostDateFormat( $id );
		return $this;

	}

	/**
	 *
	 */
	public function hidePostCount() {
		$this->_showPostCount = false;
		return $this;

	}

	/**
	 * @param string $id
	 */
	public function setArchivesType( $id ) {
		$archiveTypes = array( 'yearly', 'monthly', 'daily', 'weekly', 'postbypost', 'alpha' );
		if ( in_array( $id, $archiveTypes ) ) {
			$this->_archivesType = $id;
			$this->setArchivesText( substr_replace( $id, strtoupper( substr( $id, 0, 1 ) ), 0, 1 ) . ' Archives' );
		}
		return $this;

	}

	/**
	 * @param string $id
	 */
	function setCustomPagesQuery( $id ) {
		$this->_customPagesQuery = $id;
		return $this;

	}

	/**
	 * @param string $shortcode The shortcode keyword that will be used to output the sitemap
	 */
	public function shortcode( $shortcode ) {
		add_shortcode( $shortcode, array( &$this, 'build' ) );

	}

	/**
	 * Does the main work of creating the output
	 */
	public function build() {
		foreach ( $this->_order as $section ) {

			if ( 'pages' === $section ) {
				$output .= '<' . $this->_headingLevel . '>' . $this->_pagesText . '<' . $this->_headingLevel . '>' . "\n"
						. '<ul>' . "\n" . wp_list_pages( 'echo=0&show_date=' . $this->_showPageDate . '&date_format=' . $this->_pagesDateFormat . '&title_li=&' . $this->_customPagesQuery ) . '</ul>' . "\n";
			}

			if ( 'posts' === $section ) {
				$output .= '<' . $this->_headingLevel . '>' . $this->_postsText . '<' . $this->_headingLevel . '>' . "\n"
						. '<ul>' . "\n" . $this->_posts_by_category() . '</ul>' . "\n";
			}

			if ( 'archives' === $section ) {
				$output .= '<' . $this->_headingLevel . '>' . $this->_archivesText . '<' . $this->_headingLevel . '>' . "\n"
						. '<ul>' . "\n" . wp_get_archives( 'type=' . $this->_archivesType . '&echo=0&show_post_count=' . $this->_showPostCount ) . '</ul>' . "\n";
			}
		}
		return $output;

	}

	protected function _posts_by_category() {
		global $wpdb, $post;
		$tp = $wpdb->prefix;
		$sort_code = 'ORDER BY name ASC, post_date DESC';
		$the_output = NULL;
		$last_posts = (array) $wpdb->get_results( "SELECT {$tp}terms.name, {$tp}terms.term_id, {$tp}term_taxonomy.term_taxonomy_id	FROM {$tp}terms, {$tp}term_taxonomy	WHERE {$tp}terms.term_id = {$tp}term_taxonomy.term_id AND {$tp}term_taxonomy.taxonomy = 'category'" );

		if ( ! $last_posts )
			return;

		$the_output .= '';
		$used_cats = array( );
		$i = 0;

		foreach ( $last_posts as $posts ) {
			if ( in_array( $posts->name, $used_cats ) )
				unset( $last_posts[$i] );
			else
				$used_cats[] = $posts->name;

			$i++;
		}

		$last_posts = array_values( $last_posts );

		foreach ( $last_posts as $posts ) {
			$the_output .= '<li><a href="' . get_page_link( $posts->term_id ) . '"><strong>' . apply_filters( 'list_cats', $posts->name, $posts ) . '</strong></a><ul>';
			$arcresults = $wpdb->get_results( "SELECT * FROM $wpdb->posts WHERE post_type = 'post' AND post_status = 'publish' AND ID IN (SELECT object_id FROM {$tp}term_relationships, {$tp}terms WHERE {$tp}term_relationships.term_taxonomy_id =" . $posts->term_taxonomy_id . ") ORDER BY post_date DESC" );
		    foreach ( $arcresults as $arcresult ) {
			    $the_output .= '<li><a href="' . get_page_link($arcresult->ID) . '">' . apply_filters('the_title', $arcresult->post_title) . '</a>';
				if ($this->_showPostDate)
					$the_output .= date($this->_postsDateFormat,strtotime($arcresult->post_date));
				$the_output .= '</li>';
			}
			$the_output .= '</ul></li>';
		}
		return $the_output;
	}

}