A quick and painless way to remove the width from a wordpress caption and optionally add a source link as nofollow

functions.php

// Originally built for http://www.mybanktracker.com/bank-news/
function mbt_img_caption_shortcode($val, $attr, $content = null) {
	extract(shortcode_atts(array(
		'id'	=> '',
		'align'	=> 'alignnone',
		'width'	=> '',
		'caption' => ''
	), $attr));

	// if it contains a pipe character, we know it's ours
	if (strpos($caption, '|') === FALSE) {
		return;
	}

	$tokens = explode('|', $caption);
	$caption = array_shift($tokens);
	$href = implode('|', $tokens);
	if (!empty($href)) {
		$caption .= ' <a href="' . $href . '" rel="nofollow">source</a>';
	}

	if ( 1 > (int) $width || empty($caption) )
		return $content;

	if ( $id ) $id = 'id="' . esc_attr($id) . '" ';

	return '<div ' . $id . 'class="wp-caption ' . esc_attr($align) . '">'
	. do_shortcode( $content ) . '<p class="wp-caption-text">' . $caption . '</p></div>';
}

// what is 10, 3 for?
add_filter('img_caption_shortcode', 'mbt_img_caption_shortcode', 10, 3);