Displaying unique sidebar for Archives

You’ll see on all my main pages, on the left hand side there is the title of the page and a mini description on the graphic of a noticeboard. For example: Big Blogs
“You’re at my blog main page. Here you can follow my journey as it happens and view all archived posts to follow the journey so far.”

I would like to feature a different one on each of my archives page. i.e. relate the sidebar to a unique post (which I can edit on the backend)
For example: http://www.thebreadcrumbtrail.org/archives/category/travel-australia

I have tried adding

if ( is_archive ()) { ?> <?php $post_id = 39;
$queried_post = get_post($post_id); echo $queried_post->post_content;?> <?php } ?>

to my sidebar.php, but it did not work.

I have however noticed, that I have one archive.php file, yet my posts are filed under “archives” e.g. http://www.thebreadcrumbtrail.org/archives/date/2009/12

Here is my sidebar .php:

<?php /* Local File */ ?>

<!-- sidebar start -->
	  <div id="sidebar">
			<p>&nbsp;</p>
			<p>&nbsp;</p>
			<p>&nbsp;</p>
			<p>&nbsp;</p>
			<p>&nbsp;</p>

		<div class="intro">

			<?php if (is_page('home')) { ?> <?php $post_id = 11;
				$queried_post = get_post($post_id); echo $queried_post->post_content;?> <?php } ?>
			<?php if (is_home()) { ?> <?php $post_id = 19;
				$queried_post = get_post($post_id); echo $queried_post->post_content;?> <?php } ?>
			<?php if (is_page('Trails')) { ?> <?php $post_id = 25;
				$queried_post = get_post($post_id); echo $queried_post->post_content;?> <?php } ?>
			<?php if (is_page('ESE Travel')) { ?> <?php $post_id = 31;
				$queried_post = get_post($post_id); echo $queried_post->post_content;?> <?php } ?>
			<?php if (is_page('Gallery')) { ?> <?php $post_id = 36;
				$queried_post = get_post($post_id); echo $queried_post->post_content;?> <?php } ?>
			<?php if (is_page('Crumbs About Us')) { ?> <?php $post_id = 5;
				$queried_post = get_post($post_id); echo $queried_post->post_content;?> <?php } ?>
			<?php if (is_page('Links')) { ?> <?php $post_id = 39;
				$queried_post = get_post($post_id); echo $queried_post->post_content;?> <?php } ?>
			if ( is_page('archives')) { ?> <?php $post_id = 39;
				$queried_post = get_post($post_id); echo $queried_post->post_content;?> <?php } ?>

			<p>&nbsp;</p>
			<p>&nbsp;</p>
			<p>&nbsp;</p>
			<p>&nbsp;</p> 

		</div>

			<div id="sidebar_top"></div>
			<ul>
			<?php if ( !function_exists('dynamic_sidebar') || !dynamic_sidebar('Left Sidebar') ) : ?>
				<li>
					<h3>Categories</h3>
					<ul>
						<?php wp_list_cats('sort_column=name&optioncount=0&hierarchical=0'); ?>
					</ul>
				</li>
				<li>
					<h3>Archives</h3>
					<ul>
						<div id="archives">
<select name="archive-dropdown" onChange='document.location.href=this.options[this.selectedIndex].value;'>
  <option value=""><?php echo attribute_escape(__('Select Month')); ?></option>
  <?php wp_get_archives('type=monthly&format=option&show_post_count=1'); ?> </select>
						</div>

					</ul>
				</li>

				<li>
					<h3>Meta</h3>
					<ul>
						<?php wp_register(); ?>
						<li><?php wp_loginout(); ?></li>
						<li><a href="http://validator.w3.org/check/referer">Valid <abbr title="eXtensible HyperText Markup Language">XHTML</abbr></a></li>
						<li><a href="http://gmpg.org/xfn/"><abbr title="XHTML Friends Network">XFN</abbr></a></li>
						<?php wp_meta(); ?>
					</ul>
				</li>
			<?php endif; ?>
			</ul>
	  </div>
<!-- sidebar end -->

Any ideas?

Thanks in advance

James