I actually just added that to my todo list yesterday! I was looking at WordPress.com…
Simple Plus („+“) Shortcode
function plus_func($atts) {
extract( shortcode_atts( array(
'symbol' => '+++',
), $atts ) );
$return = '<span class="symbol">'.$symbol.'</span>';
return $return;
}
add_shortcode('plus','plus_func');