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.

Jonas

This will give you an advanced pagination to distribute your link-juice more evenly across your paginated paged. It also provides a better choice of navigation to the user to explore and find your content.
You can turn the pagination on/off separately for:
<ul>
<li>homepage</li>
<li>search results</li>
<li>category archives</li>
<li>date archives</li>
<li>tag archives</li>
<li>author archives</li>
</ul>
Or implement it directly into your theme using <code><?php the_wp_lopa('pages_below'); ?></code>.
You can also choose if you want it to be displayed before and/or after the loop content.
The plugin is currently available in English and German. If you want to help translate it, just write me an email. Help is much appreciated!
For more information visit the <a href="http://www.k308.de/labs/logarithmic-pagination" title="Logarithmic Pagination plugin page" rel="nofollow ugc">plugin website</a>.
<h4>Credits</h4>
This plugin is based on the idea found in the following (German) article by Nikolas Schmidt-Voigt: <a href="http://www.kawumba.de/webseitenstruktur-und-paginierung-fuer-seo/" title="Logarithmic Pagination plugin page" rel="nofollow ugc">Webseitenstruktur und Paginierung für SEO</a> & a 
<a href="http://stackoverflow.com/questions/7835752/how-to-do-page-navigation-for-many-many-pages-logarithmic-page-navigation" title="" rel="nofollow ugc">discussion</a> on stackoverflow.

Logarithmic Pagination

This plugin inserts pagination to your blog, archives and search results based on logarithmic calculation for a more evenly distributed link-juice.

Expanding Archives vs Logarithmic Pagination