WP Links Widgets Customizing

gistfile1.php

<?php
/**
 * Replace <ul> from blogroll widget with <div>.
 */
function md_replace_ul_blogroll( $output ) {
	$output = str_replace( "<ul class='xoxo blogroll'>", "<div>", $output );
	$output = str_replace( "</ul>", "</div>", $output );

	return $output;
}
add_filter( 'wp_list_bookmarks', 'md_replace_ul_blogroll' );

/**
 * Replace <li> from blogroll widget with <span>.
 */
function md_replace_li_blogroll( $args ) {
	$args['before'] = '<span>';
	$args['after'] = '</span>';

	return $args;
}
add_filter( 'widget_links_args', 'md_replace_li_blogroll' );