you could use restrict_manage_posts to add a dropdown field to the admin bar. however this code needs refining, because terms are not presented hierarchical atm.
add_action( 'restrict_manage_posts', 'my_restrict_manage_posts' );
function my_restrict_manage_posts() {
global $typenow;
$taxonomy = 'your_taxonomy_name';
if( $typenow != "page" && $typenow != "post" ){
$filters = array($taxonomy);
foreach ($filters as $tax_slug) {
$tax_obj = get_taxonomy($tax_slug);
$tax_name = $tax_obj->labels->name;
$terms = get_terms( $tax_slug, array( 'hide_empty' => false ) );
echo "<select name="$tax_slug" id='$tax_slug' class="postform">";
echo "<option value="">Show All $tax_name</option>";
foreach ( $terms as $term ) {
if ( isset( $_GET[ $tax_slug ] ) ) {
$get_tax_slug = $_GET[ $tax_slug ];
} else {
$get_tax_slug = false;
}
echo '<option value="
. $term->slug, $get_tax_slug == $term->slug ? " selected="selected"' : '','>'
. ( (int) $term->parent > 0 ? '- ' : '' ) . $term->name . '</option>';
}
echo "</select>";
}
}
}