kegentile

This plugin will create a tag cloud for a specific author. This will allow a visitor on your site to drill deep down into an author’s specific content.
It uses all of the same parameters as wp_tag_cloud(), but adds an additional one for the author_id. When the author_id is passed an integer of a published author that has tagged his or her posts, a tag cloud will be generated.
It will also create a new permalink structure on your site of
www.yoursite.com/author/author-slug/tag/tag-slug
***Note: that you must be using any custom permalink structure for this plugin to function. Also, custom taxonomies is currently not functioning with this version, please look forward for this in a later version.

Author Tag Cloud

Creates a template tag to create an author specific tag cloud and creates a new permalink structure to drill down into content by author and tag.

Waterloo Plugins

Tag Cloud Widget adds a simple tag cloud widget that you can use anywhere on your blog. This plugin looks at all your tags and displays them in a widget. The more times a tag is used, the larger the tag is.
Each tag is a link to the tag page (e.g. http://your-site.com/tag/your-tag). This will help with SEO.
Currently, there aren’t any options to customize the tag cloud. It should work well out of the box. In the future, there may be options to customize the widget.

Good

A tag cloud widget with links to your tag pages

Author Tag Cloud vs Tag Cloud Widget