Yes you can easily add a fully functional TinyMCE editor in your category and tag admin pages and use it for styling up the introductory information. CategoryTinymce plugin allows you to do so very easily.
Installation & Usage: Simply install and activate it. After activation the plugin automatically adds a TinyMCE editor in category description box present in category edit screen. Using this visual editor you can spice up your category introductory text, add images and more. The plugin also works with tags.