Wordpress intelligent Excerpt. Following function will create an excerpt from content where first sentence ends (with period) or if first sentence is too long it will only show number of characters defined in the function. in following case it'll show 200 characters.

gistfile1.php

<?php
// 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);
	}
}
?>
//Code to use in template
<?php print_excerpt(200); ?>