Some nice WP filters and functions to make posts better.

excerpt-length.php

add_filter( 'excerpt_length', 'my_excerpt_length' );
function my_excerpt_length( $length ) { 
	return 110; 
}

icon-link.css

a.prettylink-wpmudev::before {
	content: '';
	margin-right:2px;
	position:relative;
	top:2px;
	width: 16px;
	height:16px;
	background: url('http://mysite.com/wp-content/uploads/2015/03/04/wpmuico.ico');
	display:inline-block;
}

images.php

$args = array(
	'post_type' => 'attachment',
	'post_status' => 'any',
	'post_parent' => get_the_ID(),
	'posts_per_page' => -1,
	'fields' => 'ids';
);
$images = new WP_Query( $args );
echo do_shortcode( '[gallery ids="' . implode( ',', $images ) . '"]' );

insert.php

add_filter( 'the_content', 'my_content_insertion' );

function my_content_insertion( $content ) {

	preg_match_all('/<\/p>/', $content,$matches, PREG_OFFSET_CAPTURE);  
	$insertion_point = $matches[0][1][1];

    $content_before = substr( $content, 0, $insertion_point + 4 );
    $content_after = substr( $content, $insertion_point + 5 );

    $content_to_insert = get_the_post_thumbnail( $post->ID, 'post-single' );

    return $content_before . $content_to_insert . $content_after;

}

outdated.php

add_filter( 'the_content', 'outdated_notice' );
function outdated_notice( $content ) {
	$notice = "<p class='notice'>This content is more than a year old, it may be outdated!</p>";

	$post_time = get_the_time( 'U' );
	$current_time = current_time( 'timestamp' );

	if( $current_time - $post_time >= 31556926 ) {
		$content = $notice . $content;
	}

	return $content;

}

redact.php

add_filter( 'the_content', 'my_redaction' );
function my_redaction( $content ) {

	$search = array(
		'frak' => '<span class="redacted">karf</span>',
	);

	$content = str_replace( array_keys( $search ), $search, $content );

	return $content;

}

redirect.php

add_action( 'template_redirect', 'single_result' );
function single_result() {
    if ( is_search( )) {
        global $wp_query;
        if ( $wp_query->post_count == 1 ) {
            wp_redirect( get_permalink( $wp_query->posts['0']->ID ) );
        }
    }
}

replace-content.php

function auto_link_text( $content ){

	$replacements = array(
    	'WordPress' => '<a href="http://wordpress.org">WordPress</a>'
	);
	
	$content = str_replace( array_keys( $replacements ), $replacements, $content );

	return $content;
}

add_filter( 'the_content', 'auto_link_text' );

shortcodes.php

add_shortcode( 'iconlink', 'iconlink' );
function iconlink( $atts ) {
	$atts = shortcode_atts( array(
		'url' => false,
		'text' => 'link'
	), $atts );

	if( empty( $atts['url'] ) ) {
		return;
	}

	$url = parse_url( $atts['url'] );
	$domain = str_replace( '.', '-', $url['host'] );
	
	return '<a href="' . $atts['url'] . '" class="' . $domain . '">' . $atts['text'] . '</a>';

}

add_shortcode( 'update_notice', 'update_notice' );
function update_notice( $atts ) {
	$atts = shortcode_atts( array(
		'url' => false,
	), $atts );
	
	if( empty( $atts['url'] ) ) {
		return;
	}

	return 'This post is a bit outdated so we have updated the contents 
	with new developments and new methods. Please read <a href="' . $atts['url'] . '">the new version</a> for more information';
}