Find Friends Who Use WordPress > http://en.blog.wordpress.com/2012/05/01/find-friends/
Getting More Views and Traffic > http://en.support.wordpress.com/getting-more-views-and-traffic/
For WordPress.com global tag searches ie. Topics search to locate blogs with similar content see here > http://wordpress.com/#!/read/topics/
For WordPress.com searches
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 Google searches use this format and replace "keyword" with whatever word you wish:
keyword site:wordpress.com/
Example search string
Queen Victoria site:wordpress.com
results > http://tinyurl.com/csaobsx
On the bottom of your Admin page you will find a link to the Learn WordPress.com blogging Tutorial prepared by Staff. http://learn.wordpress.com/
The support documentation is all found at the Support link http://en.support.wordpress.com which is also on the bottom of your Admin page.