Tagging the content has increased the searchability of content in todays Web 2.0 world. Also similar content can be grouped together by assigning them same tags.
Tag Cloud has became a good way of displaying the weighted tags in a manner easy to understand and search. You can find a lot of code written in all possible scripts to generate tag clouds. You may interested in Generating tag cloud with PHP and MySQL.
While roaming around on internet, I found this really cool jQuery plugin jsTagCloud that generates 3D tag cloud!! The result is quite impressive and you can actually move the tag cloud using mouse pointer. It uses the canvas element to render a 3d cloud that can be rotated with the mouse.
Following is the demo and code that I used to generate 3D tag cloud using jsTagCloud plugin.