This plugin can add rel=”noindex,nofollow” to archive, tag, and category links. You can configure exactly which links are given which attributes. For instance, you could add rel=”noindex,nofollow” to all of your tag links, rel=”noindex” to all of your archive links, and nothing to your category links.

Noindex/Nofollow links

This plugin can add rel="noindex,nofollow" to archive, tag, and category links. You can configure exactly which links are given which attrib …

Badi Jones

Duplicate Content Cure is an extremely simple plugin that makes WordPress more Search Engine 
friendly (And therefore improving SEO). It does this by preventing search engine spiders/bots 
from accessing pages like Archives, Tags, and Categories, which tend to contain duplicated content 
from elsewhere on your site. This is achieved by adding nofollow, noindex to 
these problem pages.
Duplicate Content Cure doesn’t have a lot of features that other SEO plugins have, but 
it also is lightning fast by comparison.

Duplicate Content Cure

Duplicate content cure is a simple plugin that improves SEO by preventing search engines from indexing pages that contain duplicate content.

Noindex/Nofollow links vs Duplicate Content Cure