Hi Gert,
I'm not sure of a plugin or a widget, but there is WordPress custom code that you can use. For example, the query_posts command. You just query the posts and then set up however you'd like the items displayed. See:
Template Tags/query posts « WordPress Codex
Example:
Code:
<?php query_posts('category_name=special_cat&showposts=10'); ?>
<?php while (have_posts()) : the_post(); ?>
<a href="<?php the_permalink(); ?>> <?php the_title(); ?></a><br />
<?php endwhile;?>
This will show the title of each post as the link to the post, for the last 10 posts (each seperated by a line break) in the category named "special_cat."