slaptijack

Suggest Tags creates a list of tag suggestions based on the content of the post you are editing. Since the Yahoo! Term Extraction API is going to be shutdown at the end of August 2009, this plugin uses the term extraction API from tagthe.net.

Suggest Tags

Suggest Tags uses the tagthe.net tagging web service to generate a list of tag suggestions.

antonioandra.de

Enables your blog readers to suggest new post tags or upvote/downvote existing ones. 
Downvoted tags are eventually removed. 
A few more features are on the works as is the expansion of this readme document.
<h3>RoadMap</h3>
Add some frontend feedback; 
Add support for custom taxonomy tagging; 
Synonym dictionary; 
Better documentation, ui and automatic integration.

Author: António Andrade

Enables your blog readers to suggest new post tags or upvote/downvote existing ones.

Suggest Tags vs Author: António Andrade