The above screenshot should illustrate what the little extension does. The following code must be put in a Plugin or be copied into the functions.php of the theme.

if ( !function_exists('fb_AddThumbColumn') && function_exists('add_theme_support') ) {

	// for post and page
	add_theme_support('post-thumbnails', array( 'post', 'page' ) );

	function fb_AddThumbColumn($cols) {

		$cols['thumbnail'] = __('Thumbnail');

		return $cols;
	}

	function fb_AddThumbValue($column_name, $post_id) {

			$width = (int) 35;
			$height = (int) 35;

			if ( 'thumbnail' == $column_name ) {
				// thumbnail of WP 2.9
				$thumbnail_id = get_post_meta( $post_id, '_thumbnail_id', true );
				// image from gallery
				$attachments = get_children( array('post_parent' => $post_id, 'post_type' => 'attachment', 'post_mime_type' => 'image') );
				if ($thumbnail_id)
					$thumb = wp_get_attachment_image( $thumbnail_id, array($width, $height), true );
				elseif ($attachments) {
					foreach ( $attachments as $attachment_id => $attachment ) {
						$thumb = wp_get_attachment_image( $attachment_id, array($width, $height), true );
					}
				}
					if ( isset($thumb) && $thumb ) {
						echo $thumb;
					} else {
						echo __('None');
					}
			}
	}

	// for posts
	add_filter( 'manage_posts_columns', 'fb_AddThumbColumn' );
	add_action( 'manage_posts_custom_column', 'fb_AddThumbValue', 10, 2 );

	// for pages
	add_filter( 'manage_pages_columns', 'fb_AddThumbColumn' );
	add_action( 'manage_pages_custom_column', 'fb_AddThumbValue', 10, 2 );
}

if ( function_exists('register_sidebar') ) {
    register_sidebar(array(
        'name' => 'My Lorem Ipsum Sidebar',
        'description' => __('Sed ut perspiciatis unde omnis iste natus error sit voluptatem accusantium doloremque laudantium, totam rem aperiam, eaque ipsa quae ab illo inventore veritatis et quasi architecto beatae vitae dicta sunt explicabo.', 'your_textdomain'),
        'before_widget' => '<li id="%1$s" class="widget %2$s">',
        'after_widget' => '</li>',
        'before_title' => '<h2 class="widgettitle">',
        'after_title' => '</h2>',
    ));
}

A more comprehensive example with two widget areas, one area for the sidebar and an area for the footer.

if ( function_exists('register_sidebar') ) {
    register_sidebar(array(
        'id' => 'sidebar',
        'name' => 'My Lorem Ipsum Sidebar',
        'description' => __('Sed ut perspiciatis unde omnis iste natus error sit voluptatem accusantium doloremque laudantium, totam rem aperiam, eaque ipsa quae ab illo inventore veritatis et quasi architecto beatae vitae dicta sunt explicabo.', 'your_textdomain'),
        'before_widget' => '<li id="%1$s" class="widget %2$s">',
        'after_widget' => '</li>',
        'before_title' => '<h2 class="widgettitle">',
        'after_title' => '</h2>',
    ));

    register_sidebar(array(
        'id' => 'footer',
        'name' => 'My Lorem Ipsum Footer',
        'description' => __('Sed ut perspiciatis unde omnis iste natus error sit voluptatem accusantium doloremque laudantium, totam rem aperiam, eaque ipsa quae ab illo inventore veritatis et quasi architecto beatae vitae dicta sunt explicabo.', 'your_textdomain'),
        'before_widget' => '<li id="%1$s" class="widget %2$s">',
        'after_widget' => '</li>',
        'before_title' => '<h2 class="widgettitle">',
        'after_title' => '</h2>',
    ));
}

This may be used as follows in the templates, it's being used in the footer.php of the widget area My Lorem Ipsum Footer.

<div id="footer">
    <ul>
        <?php dynamic_sidebar('footer'); ?>
    </ul>
</div>

You can provide 4 picture formats to the function (change the width and height values to your need):

// the thumbnail
the_post_thumbnail(array(100,100)); 

// medium resolution
the_post_thumbnail(array(300,200));

// large resolution
the_post_thumbnail(array(600, 400));

// original
the_post_thumbnail();

You can set how the images should align. It is also possible to assign an own class:

//  left align
the_post_thumbnail(array(100,100), array('class' => 'alignleft'));

//  right align
the_post_thumbnail(array(100,100), array('class' => 'alignright'));

//  center
the_post_thumbnail(array(100,100), array('class' => 'aligncenter'));

// align right and the class  'my_own_class'
the_post_thumbnail(array(100,100), array('class' => 'alignright my_own_class'));

The 3rd possibility is the control of the images size with an array of height and width:
For this purpose we suppose that the settings for thumbnail is 150x150, for medium 300x200 and for large 600x400.

// thumbnail scaled to 60x60 pixel
the_post_thumbnail(array(60,60), array('class' => 'alignleft')); 

// original thumbnail
the_post_thumbnail(array(150,150), array('class' => 'alignleft'));

// medium resolution scaled to 200x133 pixel
the_post_thumbnail(array(200,200), array('class' => 'alignleft'));

// large resolution scaled to 400x266 Pixel
the_post_thumbnail(array(400,345), array('class' => 'alignleft'));

We see that the image proportions are always maintained, even if one specifies crooked values.

For the Theme Designers is this not necessarily easier, because no one knows what the user will put in his settings o his library. One way to approach this problem, to query the options for the various sizes:

// width of the thumbnails
get_option('thumbnail_size_w');

//  height of the thumbnails
get_option('thumbnail_size_h');

//  height of the medium resolution
get_option('medium_size_h');

//  width of the large resolution
get_option('large_size_w');

//  1 = Crop thumbnail to exact dimensions, 0 = Crop off
get_option('thumbnail_crop')

You can change these values in your theme.

$w = get_option('thumbnail_size_w') / 2;
$h = get_option('thumbnail_size_h') /2;

the_post_thumbnail(array($w, $h), array('class' => 'alignleft'));

Here another example: If the size of a thumbnail is bigger than 100x100 and crop is activated, then the thumbnail should be resized to 100x100, otherwise use the original thumbnail.

if(get_option('thumbnail_size_w') > 100 && get_option('thumbnail_crop') == 1) {
    the_post_thumbnail(array(100,100));
}else{
    the_post_thumbnail('thumbnail');
}

Have fun with post thumbnails! But be aware, that each post thumbnail requires 2 data base queries. On a page with 10 posts that would be 20 more queries.

<?php
function my_new_contactmethods( $contactmethods ) {
  // Add Twitter
  $contactmethods['twitter'] = 'Twitter';
  //add Facebook
  $contactmethods['facebook'] = 'Facebook';

  return $contactmethods;
}
add_filter('user_contactmethods','my_new_contactmethods',10,1);
?>

This function does nothing more than expand the array $contactmethods with the fields twitter and facebook. The value behind the fields is used as a label for the input fields. You can also remove existing fields, here the field of YAHOO IM:

  // Remove Yahoo IM
  unset($contactmethods['yim']);

This fields can be displayed on the author page.

<?php
$current_author = get_userdata(get_query_var('author'));
?>
<p><a href="<?php echo esc_url($current_author->twitter);?>" title="Twitter"> Follow me on Twitter</a></p>

Alternatively you can also use the template tag the_author_meta.

the_author_meta('facebook', $current_author->ID)

That's all behind the 16ht door of our Advent Calendar. Have fun expanding your contact fields.

function wpe_excerptlength_teaser($length) {
    return 45;
}
function wpe_excerptlength_index($length) {
    return 30;
}
function wpe_excerptmore($more) {
    return '...';
}

Now the new excerpt function.

function wpe_excerpt($length_callback='', $more_callback='') {
    global $post;
    if(function_exists($length_callback)){
        add_filter('excerpt_length', $length_callback);
    }
    if(function_exists($more_callback)){
        add_filter('excerpt_more', $more_callback);
    }
    $output = get_the_excerpt();
    $output = apply_filters('wptexturize', $output);
    $output = apply_filters('convert_chars', $output);
    $output = '<p>'.$output.'</p>';
    echo $output;
}

This function will be given the two filter functions. It will examine whether those features are available and if so, we applied the filter. Isn't there a length function, then WordPress applies the default value of 55 words. Thereafter, the excerpt will be taken. Then additional filters are applied (see default_filters.php). I haven't used the filter convert_smilies, it doesn't work with automatic excerpts anyways and I personally do not like wpautop because it comes with unpredictable results, especially in lists or code. That's why I wrapp the outputs with a clause.

Now we need the function in the template.

<?php wpe_excerpt('wpe_excerptlength_index', 'wpe_excerptmore'); ?>
// the other one
<?php wpe_excerpt('wpe_excerptlength_teaser', 'wpe_excerptmore'); ?>

Now, it makes no sense to write for any value of 1-55, a filter function , but for 2-3 different values in different views, the solution is useful.

WordPress Trash will have it's premiere in version 2.9. Now you can move every content, comment, post, pages, media and link to trash. It's quite the same function as you know from other online applications or operating systems.

If you like to configure a special date of how long files should be kept in your trash, you can configure it in your wp-config.php.
define( 'EMPTY_TRASH_DAYS', 10 );

The default settings deletes your content after 30 days. If you don't want to use trash at all, just use the value 0.

define('EMPTY_TRASH_DAYS', 0);

Now there is no trash in your admin area available, and also no links to move files to your trash.

In previous versions of WordPress 2.9, the intergration is easy to do:

<?php if ( is_singular() ) echo '<link rel="canonical" href="' . get_permalink() . '" />'; ?>

Putting it in the header.php of the theme is the easiest way to have the link-tag in the head of your frontend.

Since WordPress 2.9 it won't be necessary because WordPress set with the help of the default filter, see wp-includes/default-filters.php, the link-tag to the hook wp_head.

add_action( 'wp_head', 'rel_canonical' );

Thereby it calls the function rel_canonical(), which simply writes the HTML and passes the link of the article. Alternatively you can disable the filter and you can use it yourself.

remove_action( 'wp_head', 'rel_canonical' ); // to delete in head

... which you can activate with the help of a constant; stored in wp-config.php, you have access to the script.

define('WP_ALLOW_REPAIR', true);

Call the script from the outside at the following address ...
http://example.com/wp-admin/maint/repair.php

... where you either repair the database or run the optimization. Technically, there is no magic behind this work, but the familiar SQL statements ANALYZE TABLE, REPAIR TABLE and OPTIMIZE TABLE.

I guess that will start a debate, why with the constant and why from the outside, etc. - leave your comment here. Alternatively, anyone can contribute to WordPress and discuss directly with the developers or enter changes directly to the code.

// Load in support for template functions which the theme supports
require_if_theme_supports( 'post-thumbnails', ABSPATH . WPINC . '/post-image-template.php' );

In functions.php it queries whether the theme supports post-thumbnail function:

if ( function_exists( 'add_theme_support' ) )
	add_theme_support( 'post-thumbnails' );

If you look at the file wp-includes/post-image-template.php, there are 4 new features:

• has_post_image()
• get_post_image_id()
• the_post_image()
• get_the_post_image()

The theme itself can check within the loop, if the post has a Post-Thumbnail, and if so, then it can be output:

<?php if ( has_post_image() ) : ?>
	<a href="<?php the_permalink(); ?>"><?php the_post_image( array( 75, 75 ), array( 'class' => 'alignleft' ) ); ?></a>
<?php endif; ?>

Those interested in more features and information should check the file in WordPress 2.9: wp-includes/post-image-template.php
Especially the function: get_the_post_image
It allows to adjust the output by using hooks.
In get_the_post_image the function wp_get_attachment_image get also used, what has been explained in detail in this post just a few days ago.

WordPress 2.9 will have the possibility to update all your Plugins, which have an update available, in one step.
That makes maintenance work with customer's and on your own blog more simple and faster. As a little insight, here is a screenshot of the current beta.