Allow HTML in Excerpts

function wp_trim_excerpt($text) { // Fakes an excerpt if needed
    global $post;
    if ( '' == $text ) {
        $text = get_the_content('');
        $text = apply_filters('the_content', $text);
        $text = str_replace('\]\]\>', ']]>', $text);
        $text = strip_tags($text);
        $excerpt_length = 55;
        $words = explode(' ', $text, $excerpt_length + 1);
        if (count($words)> $excerpt_length) {
            array_pop($words);
            array_push($words, '[...]');
            $text = implode(' ', $words);
        }
    }
    return $text;
}

function lt_html_excerpt($text) { // Fakes an excerpt if needed
    global $post;
    if ( '' == $text ) {
        $text = get_the_content('');
        $text = apply_filters('the_content', $text);
        $text = str_replace('\]\]\>', ']]>', $text);
        /*just add all the tags you want to appear in the excerpt --
        be sure there are no white spaces in the string of allowed tags */
        $text = strip_tags($text,'<p><br><b><a><em><strong>');
        /* you can also change the length of the excerpt here, if you want */
        $excerpt_length = 55; 
        $words = explode(' ', $text, $excerpt_length + 1);
        if (count($words)> $excerpt_length) {
            array_pop($words);
            array_push($words, '[...]');
            $text = implode(' ', $words);
        }
    }
    return $text;
}

/* remove the default filter */
remove_filter('get_the_excerpt', 'wp_trim_excerpt');

/* now, add your own filter */
add_filter('get_the_excerpt', 'lt_html_excerpt');