<?php
            // set up taxonomies
            $tax_one = 'service_categories';
            $post_type = 'services';

            $categories = get_categories( array(
            'post_type'                     => $post_type,
            'orderby'                  => 'name',
            'order'                    => 'ASC',
            'hide_empty'               => 1,
            'hierarchical'             => 1,
            'taxonomy'                 => $tax_one ));

            foreach ( $categories as $category ) : // list all categories

                echo '<h2><a href="'.get_term_link( $category->slug, $tax_one ).'">'.$category->name.'</a></h2>'?>

                <?php

                $args['tax_query'] = array(
                    array(
                        'taxonomy' => $tax_one,
                        'terms' => array($category->slug),
                        'field' => 'slug'
                    ),
                );

                $loop = new WP_Query( $args );
                if ( $loop->have_posts() ) :

                ?>

                    ...loop stuff here

                <?php endif; ?>

            <?php endforeach; ?>