Modify wp_dropdown_categories() to support taxonomy->slug in select output, and not taxonomy->id.

better wp_dropdown_categories() for taxonomies

<?php
/* 
Background: My company post type needed a filter added via the 'restrict_manage_posts' action, and I needed to modify the wp_dropdown_categories to output the taxonomy slug into the <option value="..."> instead of the taxonomy ID. The taxonomy being 'industry'. 

The SH_Walker_TaxonomyDropdown() can be found here: https://gist.github.com/2902509
*/

 function restrict_listings_by_taxonomy() {
    global $typenow;
    global $wp_query;
    if ($typenow == 'company' ) {
    $taxonomy = 'industry';
    $current_taxonomy = get_taxonomy($taxonomy);
    wp_dropdown_categories(
        array(
            'walker'=> new SH_Walker_TaxonomyDropdown(),
            'value'=>'slug',
            'show_option_all' =>  __("Show All {$current_taxonomy->label}"),
            'taxonomy'        =>  $taxonomy,
            'name'            =>  'industry',
            'orderby'         =>  'name',
            'selected'        =>  $wp_query->query['term'],
            'hierarchical'    =>  true,
            'depth'           =>  3,
            'show_count'      =>  true, // Show # companies in parents
            'hide_empty'      =>  true, // Don't show companies w/o listings
            )
        );
    }
 }

This is great, thanks for sharing.