A stripped down uni-purpose version of my magpierss hack. All it does is read feeds from Gallery and put thumbs in your sidebar. Here's the short version. Step one: get [url=http://magpierss.sourceforge.net/]magpierss[/url] and put the extlib folder and 4 rss_ files in your skins/skinname folder. Step two: put something like

<?php require( dirname(__FILE__).'/rss_fetch.inc' ); ?>
<div class="bSideItem">
<h3>Magpie Does Gallery</h3>
<?php 
$url = "http://blahblahblah.tld/gallery/rss.php";
$rss = fetch_rss($url);
require( dirname(__FILE__).'/_galleryreader.php' );
?>
</div>

in your sidebar in _main.php. Step C is to put

<?php 
/**
 * This file uses magpierss (magpierss.sourceforge.net) to read feeds from
 * gallery (gallery.menalto.com) and display a thumbnail in the sidebar.
 *
 * This requires magpieRSS which is not part of the b2evolution distribution
 * magpieRSS is released under the GPL License and the author holds copyright
 * This application makes absolutely no modifications to the magpieRSS files!
 * Download it, unzip it, and upload the files to your /skins/skinname folder
 *
 * magpieRSS - {@link http://magpierss.sourceforge.net/}
 * Released under the GNU General Public License.
 * @copyright (c)2002 kellan @ protest.net. All rights reserved.
 * Please read the disclaimer at the top of the /extlib/Snoopy.class.inc file.
 *
 * Gallery - {@link http://gallery.menalto.com/}
 * Released under the GNU General Public License.
 * @copyright (c)2000-2004 Bharat Mediratta
 * 
 * b2evolution - {@link http://b2evolution.net/}
 * Released under GNU GPL License - {@link http://b2evolution.net/about/license.html}
 * @copyright (c)2003-2004 by Francois PLANQUE - {@link http://fplanque.net/}
 *
 * @package evoskins
 * @subpackage your_skin_name
 */

if( !defined('DB_USER') ) die( 'Please, do not access this page directly.' );

# set this to false if you don't want to show the name of the gallery
# if false then 'gallery_start', 'gallery_end' and 'gallery_linked' don't get used
$show_site_name = true;
# this is for the name of the gallery
$gallery_start = '<h4>';
$gallery_end = '</h4>';
# set this to false if you don't want the gallery title linked to it's url
$gallery_linked = true;

# this is for the before and after all the thumbnails
$thumb_block_start = '';
$thumb_block_end = '';

# this is for the before and after each thumbnail
$thumb_start = '<p>';
$thumb_end = '</p>';

# set this to false if you don't want thumnails linked to thier url
$thumb_linked = true;

# this is what comes after the src and title and alt in the img tag
$thumb_tag_end = 'class="middle"';

# this is how many items to show if it is not set in _main.php
if(!isset($show_me)) $show_me = 10;

// BEYOND HERE BE DRAGONS!

if( $rss ) {

	if( $show_site_name ) { // do this if the site name gets displayed
		$site_title = $rss->channel['title'];
		$site_url = $rss->channel['link'];
		$site_desc = $rss->channel['description'];

		$gallery_string = "";
		$gallery_string .= $gallery_start;
		if( $gallery_linked ) {
			$gallery_string .= "<a href=\"".$site_url."\" title=\"".$site_desc."\">".$site_title."</a>";
			} else {
			$gallery_string .= $site_title;
			}
		$gallery_string .= $gallery_end."\n";
		echo $gallery_string;
		}

	echo $thumb_block_start."\n";
	$ii = 1;

	foreach ($rss->items as $item ) { // now start cycling through items
		if( $ii <= $show_me ) { // do it again if we have not reached the limit

			$thumb_title = $item[title];
			if( $thumb_title == '' ) { // if the item is untitled then make one up
				$thumb_title = substr(strip_tags($thumb_desc), 0, 20).'...';
				}

			$thumb_url = $item[link];
			if ( $thumb_url == '' ) { // if the item has no link then use the site link
				$thumb_url = $rss->channel['link'];
				}

			$thumb_image = $item[photo][imgsrc];
			$thumb_image = '<img src="'.$thumb_image.'" title="'.$thumb_title.'" alt="'.$thumb_title.'" '.$thumb_tag_end.' />';

			$thumb_image_string = "";
			$thumb_image_string .= $thumb_start;
			if( $thumb_linked ) { // do this if the item gets linked
				$thumb_image_string .= "<a href=\"".$thumb_url."\" title=\"link to ".$thumb_title."\">".$thumb_image."</a>";
				} else { // do this if the item title does not get linked
				$thumb_image_string .= $thumb_image;
				}
			$thumb_image_string .= $thumb_end;

			echo $thumb_image_string;
			}
		$ii++;
		}

	echo $thumb_block_end."\n";

	} else {
	echo "<p>Houston we have a problem</p>";
	}

?>

in your skins/skinname folder as _galleryreader.php.

Decorate as you see fit. I think it's got enough stuffers to let you do your thing your way. By the way I only tested this on one gallery installation. It's possible that they have more than one feed but I don't know. The file I pulled from was "rss.php" if that helps.

Finally, if you want, you can throw some traffic my way by reading the same thing on [url=http://wonderwinds.com/hackblog.php/2005/01/20/gallery_feed_reader_for_b2evolution]my blog[/url].