<?php echo do_shortcode("[my_shortcode]"); ?>

Easy and super useful.

Thanks to WP Snippets for the tip!

<?php
// Get any existing copy of our transient data
if ( false === ( $special_query_results = get_transient( 'special_query_results' ) ) ) {
    // It wasn't there, so regenerate the data and save the transient
     $special_query_results = new WP_Query( 'cat=5&order=random&tag=tech&post_meta_key=thumbnail' );
     set_transient( 'special_query_results', $special_query_results );
}

// Use the data like you would have normally...
?>

This code is using WordPress Transients API. Click here to view more useful examples of this API!

Credits: WordPress Codex.

if (!current_user_can('manage_options')) {
	add_filter('show_admin_bar', '__return_false');
}

Thanks to Jeff Starr for the tip!

// Variable & intelligent excerpt length.
function print_excerpt($length) { // Max excerpt length. Length is set in characters
	global $post;
	$text = $post->post_excerpt;
	if ( '' == $text ) {
		$text = get_the_content('');
		$text = apply_filters('the_content', $text);
		$text = str_replace(']]>', ']]>', $text);
	}
	$text = strip_shortcodes($text); // optional, recommended
	$text = strip_tags($text); // use ' $text = strip_tags($text,'<p><a>'); ' if you want to keep some tags

	$text = substr($text,0,$length);
	$excerpt = reverse_strrchr($text, '.', 1);
	if( $excerpt ) {
		echo apply_filters('the_excerpt',$excerpt);
	} else {
		echo apply_filters('the_excerpt',$text);
	}
}

// Returns the portion of haystack which goes until the last occurrence of needle
function reverse_strrchr($haystack, $needle, $trail) {
    return strrpos($haystack, $needle) ? substr($haystack, 0, strrpos($haystack, $needle) + $trail) : false;
}

Once done, you can use the print_excerpt() function in your theme files, as shown below:

<?php print_excerpt(50); ?>

Thanks to Sebastian for the function!

/**
 * Build a list of all websites in a network
 */
function wp_list_sites( $expires = 7200 ) {
   if( !is_multisite() ) return false;

   // Because the get_blog_list() function is currently flagged as deprecated
   // due to the potential for high consumption of resources, we'll use
   // $wpdb to roll out our own SQL query instead. Because the query can be
   // memory-intensive, we'll store the results using the Transients API
   if ( false === ( $site_list = get_transient( 'multisite_site_list' ) ) ) {
      global $wpdb;
      $site_list = $wpdb->get_results( $wpdb->prepare('SELECT * FROM wp_blogs ORDER BY blog_id') );
      // Set the Transient cache to expire every two hours
      set_site_transient( 'multisite_site_list', $site_list, $expires );
   }

   $current_site_url = get_site_url( get_current_blog_id() );

   $html = '
<ul id="network-menu">' . "\n";

   foreach ( $site_list as $site ) {
      switch_to_blog( $site->blog_id );
      $class = ( home_url() == $current_site_url ) ? ' class="current-site-item"' : '';
      $html .= "\t" . '
<li id="site-' . $site->blog_id . '" '="" .="" $class=""><a href="' . home_url() . '">' . get_bloginfo('name') . '</a></li>

' . "\n";
      restore_current_blog();
   }

   $html .= '</ul>

<!--// end #network-menu -->' . "\n\n";

   return $html;
}

Once done, you can use the wp_list_sites() function in your theme files. The example below shows how it works:

<?php
// Multisite Network Menu
$network_menu = wp_list_sites();
if( $network_menu ):
?>
<div id="network-menu">
   <?php echo $network_menu; ?>
</div>

<!--// end #network-menu -->
<?php endif; ?>

Thanks to Kevin Leary for the great hack!

<?php
$categories = get_terms('books_category');

for( $i=0; $i<sizeof($categories); $i++ ){
  if ( $categories[$i]->name == 'New Publications' ) :
    $latest = array($categories[$i]);
    unset($categories[$i]);
  endif;
}

if( isset($latest) )
  array_splice( $categories, 0, 0, $latest );
?>

Thanks to Sebastian for the great hack!

<?php
	$page_id = "YOUR PAGE-ID";
	$xml = @simplexml_load_file("http://api.facebook.com/restserver.php?method=facebook.fql.query&query=SELECT%20fan_count%20FROM%20page%20WHERE%20page_id=".$page_id."") or die ("a lot");
	$fans = $xml->page->fan_count;
	echo $fans;
?>

Thanks to WP Snippets for the recipe!

add_action('admin_head', 'excerpt_textarea_height');
function excerpt_textarea_height() {
    echo'
    <style type="text/css">
        #excerpt{ height:500px; }
    </style>
    ';
}

Thanks to Spyre Studios for the cool hack!

add_filter('the_content', 'wpr_google_plusone');
function wpr_google_plusone($content) {
	$content = $content.'<div class="plusone"><g:plusone size="tall" href="'.get_permalink().'"></g:plusone></div>';
	return $content;
}
add_action ('wp_enqueue_scripts','wpr_google_plusone_script');
function wpr_google_plusone_script() {
	wp_enqueue_script('google-plusone', 'https://apis.google.com/js/plusone.js', array(), null);
}

Once saved, a Google+ button will be automatically added to all your posts.

Thanks to Spyre Studios for the great piece of code!

<?php
/* Template Name: Restricted to Authors only */

if ( !current_user_can('author')) {
	wp_die('You don’t have access to this page.')
}
?>

Thanks to Kevin Chard for this snippet!