Create a dropdown list without a button to navigate custom taxonomies for custom post types

custom-taxonomy-dropdown

<?php
// place in functions or a plugin

function cpt_taxonomy_dropdown($taxonomy) { ?>
  <form action="/" method="get">
	<select name="cat" id="cat" class="postform">
	<option value="-1">Choose one...</option>
	<?php
	$terms = get_terms($taxonomy);
	foreach ($terms as $term) {
		printf( '<option class="level-0" value="%s">%s</option>', $term->slug, $term->name );
	}
	echo '</select></form>';
}

<?php 
// call it and replace the TAXONOMY with slug of custom taxonomy

cpt_taxonomy_dropdown( 'TAXONOMY' ); ?>
<script type="text/javascript"><!--
  var dropdown = document.getElementById("cat");
	function onCatChange() {
		if ( dropdown.options[dropdown.selectedIndex].value > '' ) {
			location.href = "<?php echo get_option('home'); ?>/?TAXONOMY="+dropdown.options[dropdown.selectedIndex].value;
		}
	}
dropdown.onchange = onCatChange;
--></script>