I get "tagging" but when I search tags I get famous bloggers with many fans and posts, how do I find the more obscure?
Here are your options:
The Tags search page is in the Reader area of the Dashboard.
The WordPress.com search engine indexes post, pages, and comments content (body text). Unless entered as text in those contents, blog name, post titles, and post/comment author names are not indexed. http://en.support.wordpress.com/wordpresscom-search/
For Topics (Tags page) searches see http://en.support.wordpress.com/topics/ This is the syntax http://en/wordpress.com/tags/canada
See here http://wordpress.com/#!/read/topics/
For Google searches use this format and replace "keyword" with whatever word you wish:
Example search string
Queen Victoria site:wordpress.com
results > http://tinyurl.com/csaobsx