how can I show #posts on my sidebar?

hi. on my sidebar I display categories and archives. how can I make the categories and archives display the number of posts in each category/archive as well as their respective names? e.g. a category named “folk punk” with 20 posts would show as “folk punk (20)”.

I’ve included the whole sidebar code below:

<!-- begin sidebar -->
<div id="sidebar">
<form id="searchform" method="get" action="<?php echo $_SERVER['PHP_SELF']; ?>">
			<div>
				<input type="text" name="s" value="search for..." id="s" size="15" onclick="value=''" onblur="value='search for...'" /><br />
				<? /*<input type="submit" value="<?php _e('Search'); ?>" />*/?>
			</div>
		</form>

<ul>
<?php 	/* Widgetized sidebar */
		if ( !function_exists('dynamic_sidebar') || !dynamic_sidebar() ) : ?>

	<?php wp_list_pages(); ?>
	<li id="categories"><?php _e('categories:'); ?>
		<ul>
			<?php wp_list_cats(); ?>
		</ul>
 	</li>

	<li id="archives"><?php _e('archives:'); ?>
 		<ul>
	 		<?php wp_get_archives('type=monthly'); ?>
 		</ul>
 	</li>
 	<li id="feeds"><?php _e('feeds'); ?>
 		<ul>
			<li><a href="feed:<?php bloginfo('rss2_url'); ?>" title="<?php _e('Syndicate this site using RSS'); ?>"><?php _e('<abbr title="Really Simple Syndication">RSS</abbr> Contents'); ?></a></li>
<br />

 <?php endif; ?>
</ul>
</div>
<!-- end sidebar -->