zoomer

Follow these instructions to add a Prototype lightbox to the Product Detail page.
http://www.magentocommerce.com/wiki/4_-_themes_and_template_customization/catalog/adding_lightbox_to_magento_v2

I did Step 7 differently though (Adding Lightbox to base image)
In this file \app\design\frontend\default\blank\template\catalog\product\view\media.phtml
I commented out:

<?php if ($_product->getImage() != 'no_selection' && $_product->getImage()): ?>
<p class="product-image product-image-zoom">
    <?php
        $_img = '<img id="image" src="'.$this->helper('catalog/image')->init($_product, 'image').'" alt="'.$this->htmlEscape($this->getImageLabel()).'" title="'.$this->htmlEscape($this->getImageLabel()).'" />';
        echo $_helper->productAttribute($_product, $_img, 'image');
    ?>
</p>
<p class="zoom-notice" id="track_hint"><?php echo $this->__('Double click on above image to view full picture') ?></p>
<div class="zoom">
    <img id="zoom_out" src="<?php echo $this->getSkinUrl('images/slider_btn_zoom_out.gif') ?>" alt="<?php echo $this->__('Zoom Out') ?>" title="<?php echo $this->__('Zoom Out') ?>" class="btn-zoom-out" />
    <div id="track">
        <div id="handle"></div>
    </div>
    <img id="zoom_in" src="<?php echo $this->getSkinUrl('images/slider_btn_zoom_in.gif') ?>" alt="<?php echo $this->__('Zoom In') ?>" title="<?php echo $this->__('Zoom In') ?>" class="btn-zoom-in" />
</div>
<script type="text/javascript">
//<![CDATA[
    Event.observe(window, 'load', function() {
        product_zoom = new Product.Zoom('image', 'track', 'handle', 'zoom_in', 'zoom_out', 'track_hint');
    });
//]]>
</script>
<?php else: ?>
<p class="product-image">
    <?php
        $_img = '<img src="'.$this->helper('catalog/image')->init($_product, 'image')->resize(265).'" alt="'.$this->htmlEscape($this->getImageLabel()).'" title="'.$this->htmlEscape($this->getImageLabel()).'" />';
        echo $_helper->productAttribute($_product, $_img, 'image');
    ?>
</p>
<?php endif; ?>

and put this

<?php if ($_product->getImage() != 'no_selection' && $_product->getImage()): ?>
<p class="product-image">
    <a href="<?php echo $this->helper('catalog/image')->init($_product, 'image'); ?>" rel="lightbox[rotation]" title="<?php echo $_product->getName();?>">
    <img id="image" src="<?php echo $this->helper('catalog/image')->init($_product, 'image')->resize(265,265); ?>" alt="<?php echo $this->htmlEscape($_product->getName()) ?>" title="<?php echo $this->htmlEscape($_product->getName()) ?>" />
    </a>
</p>
<?php else: ?>
<p class="product-image">
    <img id="image" src="<?php echo $this->helper('catalog/image')->init($_product, 'image')->resize(265,265); ?>" alt="<?php echo $this->htmlEscape($_product->getName()) ?>" title="<?php echo $this->htmlEscape($_product->getName()) ?>" />
</p>
<?php endif; ?>

If you get the lightbox working but the Close button image is not loading, try this.
Open \app\design\frontend\default\your_theme\template\page\html\head.phtml
and add a / inside the quotation marks of getJsSkinUrl(”)

var SKIN_URL = '<?php echo $this->helper('core/js')->getJsSkinUrl('/') ?>';