Add “current” class to sidebar item

Hello,
I would like to add a class “current” as in wp_list_pages() in my sidebar. However my sidebar is something like this:

<div id="sidebar">
<ul id="menu-1">
<li class="title"><a>Presentaci&oacute;n</a>
	<?php query_posts('category_name=presentacion'); if ( have_posts() ) : ?>
		<ul>
		<?php while ( have_posts() ) : the_post(); ?>
		<li><a href="<?php the_permalink(); ?>"><?php the_title(); ?></a></li>
		<?php endwhile; endif; ?>
        <?php wp_reset_query(); ?>
		</ul>
</li>
</ul>
</div>

and my question is how can I add e.g. class=”current” to either or when the URL matches the permalink.
To put this another way: I would like to show the visitor what post he is viewing in the sidebar by changing the style.
Any help will be appreciated.