WordPress shortcode will only display content to registered users.

members-only-shortcode.php

<?php

/**
 * WordPress shortcode only displays content to registered users.  Could be improved by
 * passing role as an attribute to only allow certain types of users.
 *
 * Example: [member]This text will be only displayed to registered users.[/member]
 */
function members_only_shortcode( $atts, $content = null ) {
    if ( is_user_logged_in() && !is_null( $content ) && !is_feed() )
	return $content;
    return '';
}
add_shortcode( 'member', 'members_only_shortcode' );