A code below displays categories in a drop-down box. I use this plugin in WordPress because it does not take up much space. It is bad because a lot of people will not click on it to display the categories. It still might be best to stick with a list of links. You have a better chance the someone clicking on a category.
<form action="<?php bloginfo('url'); ?>/" method="get"> <?php $select = wp_dropdown_categories('show_option_none=Select category&show_count=1&orderby=name&echo=0'); $select = preg_replace("#<select([^>]*)>#”, “<select$1 onchange=’return this.form.submit()’>”, $select); echo $select; ?> <noscript><input type=”submit” value=”View” /></noscript> </form>
Some people prefer having drop-down boxes to save space. But I think you should probably be more interested in having people click on links and raising your Blogs pageviews.