Tag Cloud Portlet
Starting with version 6.0 Liferay ships with a tag cloud portlet. This portlet has been designed with performance in mind, to make sure it performs well even under high load.
Another significant characteristic of the tag cloud portlet is that it's fully skinnable through CSS.
The tags cloud portlet allows navigating through the portlets in the same page that have support for it. Some examples are: Asset Publisher, Blogs, Wiki, Image Gallery and Bookmarks. Custom portlets can also add support for tags navigation using the asset framework API.
Previous versions of Liferay provide a similar portlet called tags navigation. Just like the tag cloud portlet, the tags navigation portlet allows navigating through the portlets in the same page that have support for it.