I also use wordpress as a calendar to display future events... To do so, I use this plugin :
It works well and it's very light.
You can also tweek your loop in your category page to stop display posts when the events are done... I found this piece code on this forum and it works well...
$now = current_time('mysql');
$future_posts = $wpdb->get_results("SELECT * FROM $wpdb->posts WHERE post_date > '$now' ORDER BY post_date ASC");
if($future_posts) : foreach($future_posts as $post) : setup_postdata($post);
--- DO YOUR STUFF (date, title, author, etc...) ---
<?php endforeach; ?>
<?php endif; ?>
Same thing with the RSS feed, it's also possible to don't send an event when it's done.
If you want some more information, just ask here... I use a standalone WP installation as a calendar. It's also possible to tweak the archives to show future month, the calendar to highlight and link future dates, etc, etc...