get Tag Name by ID

<?php
$posttags = get_the_tags();
if ($posttags) {
foreach($posttags as $tag) {
echo $tag->term_id . ‘, ‘;
}
}
?>

Well… get_the_tags must be used within the loop.

I have it working, this is the main part of the widget:

/** @see WP_Widget::widget */
    function widget($args, $instance) {
        extract( $args );

		$title = apply_filters('widget_title', $instance['title']);
		echo $before_widget; if ( $title )
        echo $before_title . $title . $after_title;
        $title = apply_filters('widget_title', $instance['title']);

		// get a list of ids and returns a string with term names
		$text=$instance['text'];
		$term_id_string1 = '';
		$term_id_string2 = '';
		$tag_names = explode(",", $text);
		foreach ($tag_names as $tag_name)
		{
			$aTag = get_term_by( 'name', trim($tag_name), 'post_tag' );

			if ($aTag)
			{
				$term_id_string2 .= '<a href="/about/' . trim($tag_name) . '">' . trim($tag_name) . '</a> (' . $aTag->count . '), ';
				$term_id_string1 .= $aTag->term_id . ',';
			}
		}
		//remove last comma
		$term_id_string1 = substr($term_id_string1,0,-1);
		$term_id_string2 = substr($term_id_string2,0,-2);

		// using simple tags
		//st_tag_cloud('include='.$term_id_string.'&color=false&size=false&xformat=<a href="%tag_link%" class="tag-link-%tag_id%" title="%tag_count% topics" %tag_rel% style="%tag_size% %tag_color%">%tag_name%</a> (%tag_count%)');

		// using our own tag list
		echo $term_id_string2;

		echo $after_widget;
    }

(using simple tags plugin or your own)