TagThis is a neat WordPress plugin that could be summarized as a social tagging system.
Have you ever wanted to go back and tag old posts or maybe even add more tags? TagThis is a great way to get this done. However, TagThis doesn’t just allow the author to create tags, it also allows visitors to help effectively tag articles.
According to the TagThis homepage,
TagThis is a wordpress plugin that allows the community to appropriately tag your posts. It does so by adding a small textbox below a post. The most popular tags are then added automatically to your post, and helps organize your blog. It helps you tag your old posts, or get a large database of relevant tags, and better interaction with the community.
The more a tag is recommended from various users, the higher it’s ranking on an article will be. From the plugin’s option page in your WordPress dashboard, you can see who tagged a post based on their IP address and moderate tags. The plugin also tries to help spam and gives you the option of moderating what could possible be considered "tag spam". An option for blacklisting words or IP is also available.
This is one of the neatest WordPress plugins I’ve ever come across and should be helpful to plenty of authors! My only question would be whether Technorati pays attention to these tags. What do you think?