You have plain text and link to those text in Magento Layered Navigation section. You can easily change the display of Layered Navigation links into a selection box / dropdown list. To do so, you need to edit the following file:
app/design/frontend/YOUR_PACKAGE/YOUR_THEME/template/catalog/layer/filter.phtml
filter.phtml file contains code something like below:
<ol>
<?php foreach ($this->getItems() as $_item): ?>
<li>
<?php if ($_item->getCount() > 0): ?>
<a href="<?php echo $this->urlEscape($_item->getUrl()) ?>"><?php echo $_item->getLabel() ?></a>
<?php else:
echo $_item->getLabel() ?>
<?php endif; ?>
<?php if ($this->shouldDisplayProductCount()): ?>
(<?php echo $_item->getCount() ?>)
<?php endif; ?>
</li>
<?php endforeach ?>
</ol>
Here is the edit to filter.phtml that will display selection box / dropdown list in layered navigation. You just need to replace the code of your filter.phtml file with the code shown below:
<select name="layered-nav-select" onChange="setLocation(this.value)">
<option selected="selected" value="#">Please Select</option>
<?php foreach ($this->getItems() as $_item): ?>
<?php if ($_item->getCount() > 0): ?>
<option value="<?php echo $this->urlEscape($_item->getUrl()) ?>">
<?php
echo $_item->getLabel();
if ($this->shouldDisplayProductCount()):
echo '(' . $_item->getCount() . ')';
endif;
?>
</option>
<?php else: ?>
<option value="#">
<?php
echo $_item->getLabel();
if ($this->shouldDisplayProductCount()):
echo '(' . $_item->getCount() . ')';
endif;
?>
</option>
<?php endif; ?>
<?php endforeach ?>
</select>
Now, you should be able to view selection list in your layered navigation section in frontend.
Hope this helps. Thanks.