Code:
<li><!-- Activity -->
<ul><h1><?php _e('Activity'); ?></h1>
<!--This will show the last 10 posts, including the last one. To change the number of post shown
edit the 'nuberposts=x' to whatever value you want, and to skip the last one (or last 2, 3, etc.)
increase the value of 'offset=x' (default is "0" so it will start by the last post)-->
<?php
$posts = get_posts('numberposts=10&offset=0');
foreach ($posts as $post) :
?>
<li>
<a href="<?php the_permalink(); ?>" title="<?php the_title() ?>"><?php the_title() ?></a>
</li>
<?php
endforeach;
?>
</ul>
</li><!-- End of Activity -->