The beauty of this plugin is that it has the ability to transform bbcode anywhere in Joomla. 

Joomla's normal behaviour is to either strip out any html or render the actual html markup whenever you want to add it to fields such as content item titles, menu item titles etc The YVBB plugin on the otherhand, allows you to render html markup in menu items, content titles or any other field that you can normally only affect at a deeper template level.

So when it comes to creating a two line menu item with the core Joomla menu - this plugin makes it very easy.

The following screenshot is of our Zen Default template with a small addition to the css file.

As you can see the plugin also renders the BBCode in the joomla admin.

While the code to create the menu item just looks like this - as you can see its really very simple:

Once you have the plugin and menu syntax setup then its just a matter of targeting the styles with a little css. The example above uses our Zen Default template and Ive just added the following css rule to the theme.css file to get it looking the way I wanted.

#nav  ul li a {font-size: 1.2em}

#nav ul li a em {font-size: 0.8em;color: #999}

The plugin can also (of course) render bbcode in content items and there are some very handy article linking options available also. Check out the documentation page for an overview of the other features of the plugin.