Tagxedo enables the creation of tag clouds. You can select different shapes and designs. Attention: Tagxedo does not work with every browser. I have tested it with Firefox sucessfully.
https://www.youtube.com/watch?feature=player_embedded&v=AwuB7Ub9RQU
Another tool for tag clouds is called Wordle. Wordle also allows you to analyize websites automatically.
An effective way to create a tag cloud is taggalaxy. Just fill in a word - a "tag galaxy" will be created!