Ashley

Expanding Archives adds a widget that shows your old posts in an expandable/collapsible format. Each post is categorized under its year and month, so you can expand all the posts in a given month and year.
This plugin comes with very minimal CSS styling so you can easily customize it to match your design.
JavaScript is required. No IE support.

Expanding Archives

This plugin adds a new widget where you can view your old posts by expanding certain years and months.

jonkemp

texttheater

Improves your blog’s search engine optimization by “noindexing” pages you choose.
Add the <code>noindex</code> robots meta tag to archives, categories, search pages, tags, author pages, login, admin pages or any other page you choose.
Add the <code>rel="nofollow"</code> attribute to individual pages listed by the <code>wp_list_pages</code> function or the Pages widget. Also, add the <code>rel="nofollow"</code> attribute to archive links, category links, registration and login links.
Written by Jon Kemp, currently maintained by Kilian Evang.
<h3>Usage</h3>
After installation, the settings page for this plugin can be found in your WordPress administration interface under Settings → Ultimate noindex.

Ultimate Noindex Nofollow Tool II

Improves your blog's search engine optimization by "noindexing" pages you choose. Now also for page-based (as opposed to date-based) archives.

Expanding Archives vs Ultimate Noindex Nofollow Tool II